Combi Boiler. System Drainage.

Occasionally it may be necessary to drain down a combi boiler and central heating system. This may be to facilitate maintenance procedures, cleaning the system or the addition of extra radiators.

The process is relatively simple, but prior to attempting to drain a system, it is advisable to ensure that the person carrying out the draining also knows how to re-fill, add inhibitor and pressurise the system once the work has been carried out.

The method of pressurising of a combi boiler system varies between model and manufacturer. Instructions for pressurising may be found in the boiler user’s manual.

It is important to note that if the actual boiler requires draining, this must only be carried out by a competent person. Draining a combi boiler system does not involve draining the internal part of the boiler.

Before draining the combi boiler system it is important to ensure that the mains electricity supply to the boiler and any system programmers are turned off. This is to prevent the boiler operating with an empty system, which could seriously damage the boiler.

It is not necessary to turn off the mains water supply when draining a combi boiler system.

To drain the central heating system, first, locate the drain tap. This will be on the ground floor or the lowest point of the system. Occasionally it will be conveniently located at the end of a leg of pipe leading from a radiator to the outside of the property. If not, a length of hose will need to be attached to the spigot and run to the outside of the property or to a ground level drain entrance.

With the drain tap opened, water should start to flow out of the system. This flow will need to be supported by opening up the bleed valves on all the radiators attached to the system, starting at the top of the property or the radiator furthest from the drainage tap. Air entering the system will replace the vacating central heating fluid.

With the system drained, now is a good time to flush through the central heating system to remove debris. This is best accomplished by engaging the services of a specialist company, however, some sludge and debris can be removed by operating the refilling device to allow water to flow through and out of the system. It will be necessary to close off the radiator bleed valves to facilitate the flushing through of upstairs radiators.

Once any maintenance work has been accomplished, the system can be refilled and pressurised.

Firstly, the drain tap should be closed off. It is then essential to go round all the radiators and close off the bleed valves using the radiator bleed key.

At this point, it is essential to add an inhibitor solution into the system. A good way to do this is to locate the plug at the top of one radiator. This plug will be at the opposite end to the bleed valve. Removing this screw threaded plug will reveal an opening into which the required amount of inhibitor can be added using a funnel or open-ended tube.

The correct amount of inhibitor required by the system can be calculated by using the information supplied with the inhibitor.
Do not forget to replace and firmly tighten the radiator plug after adding the inhibitor.

Water should now be allowed back into the system using the filling loop or the refilling device appropriate to the particular boiler. This may be a key type facility, which operates an internal valve system within the boiler.

As water re-enters the system, the pressure gauge on the boiler should start to register an increase in system pressure. If it does not, immediately close off the filling loop and check the entire central heating system for any leaks. It may be found that a bleed valve on a radiator has not been closed off correctly or some new work on the system is leaking.

When the pressure indicator on the boiler reads one bar, the filling loop should be turned off and all the radiators bled to remove trapped air in the system. The bleed valves on the radiators should be bled from the nearest radiator to the boiler along and up to the radiators upstairs, or the furthest from the boiler. It will be necessary to return to the boiler filling loop and re-fill the system after bleeding the air from each radiator.

With all the air removed from the system, the filling loop should be operated to pressurise the system up to the manufacturer’s recommended cold pressure operating level. This is usually between 0.5 and 1.5 bar.

Once the correct pressure is reached, the boiler power, the programmers, and the timers can be turned back on.

The boiler and central heating should now operate correctly. Any banging or loud gurgling sounds will indicate that air is still trapped within the system, as will any radiators that are hot at the base but cold at the top.

To remedy these situations, the radiators will need further bleeding to remove the trapped air.

To clean a combi boiler system, the process is similar to that described above.

First, drain down the system. Flush through with clean water. Refill with water and a suitable cleaning fluid such as Fernox. Re-pressurise the system and run for 48 hours. Drain down the system again. Flush through with clean water and refill the system with inhibitor. Finally, re-pressurise the system.

Before undertaking any DIY work on a combi boiler central heating system, it is advisable to check that the work will not invalidate any warranty on the boiler that might be in place.


The concept of zoning might seem a little complex but in all probability, if your system is a conventional indirect hot water system, you probably have a simple example of a type of zoning in operation. Hot water generated by your boiler is directed to either the domestic hot water cylinder, zone one, or the central heating, zone two. In this case, a motorised diverter valve maintains the zones.

The purpose of zoning is to optimise the domestic heating system to ensure that the different areas within the house are heated only to the required level, which in certain parts might be quite infrequently or even not at all.

In a home where a single thermostat operates to control the entire heating system, the whole house will be heated to the setting on the thermostat regardless of whether all the rooms are occupied or not, or whether they are receiving supplementary heat from sunlight or cooking tasks. The thermostat will take its base setting from its location.

Many thermostats are inadvertently placed in unsuitable positions, for example in a cold hallway or a draught, and often set to achieve an almost impossibly high temperature. This can mean that no matter how hard the boiler works, it can never reach the cut off point.

In this situation, the boiler runs continuously with some rooms cool and others uncomfortably hot.

Changes to the Buildings Regulations have been introduced to reflect the importance of conserving energy by creating zones to maximise boiler efficiency. In new builds and complete installations, the directions are mandatory and in boiler replacement situations, the directions are related to good practice.

Consequently, any new system in a home that is not based on an open plan format must have at least two heating zones. These must be individually controlled by the operation of a thermostat and a zone valve. Radiators must have Thermostatic Radiator Valves (TRV’s) fitted except those in rooms with a room thermostat installed and radiators and towel rails in bathrooms.

When replacing a boiler in an existing system it is now good practice to install TRV’s on all radiators, except those in rooms with a room thermostat and those in a bathroom. These should be installed whilst the system is drained down.

Although the generalised instructions in the Buildings Regulations will provide a good basic system of zoning, it is in a homeowner’s interest to plan and develop a zoning system that reflects the requirements of the house occupants.

Installing a timer in a two-zone system can control when heat is delivered to a particular zone independently of the zone thermostats. An example would be a timer, which responds to the expected household activity in the living or cooking areas of the property during the day and then redirects heat to the bedroom zone area at night.

Rather than settling for a simple two zone system, usually zone one, ground floor, and zone two second and subsequent floors, a multi zone system can be constructed to take into account the life-styles and commitments of various members of the household.

By installing motorised diverter valves, each operated by an individual thermostat and timer, zoning can be fine-tuned to allow each zone, possibly as individual rooms, to be controlled with precision. The motorised diverter valves will open and close to provide heat only when it is required. Consequently, the boiler will operate only as needed and in a controlled and efficient manner.

Motorised diverter valves can be fitted with wireless controls and can be operated and programmed along with their individual thermostats and timers from a central control programmer.

For a complete and remotely controlled system of zone and room control, TRV’s are relatively good at regulating individual radiators. They are also ideal for regulating temperatures in different areas, for example a cooler bedroom for sleeping in and a warm living area for relaxing in.

New wireless controlled examples can be remotely controlled from a central programmer, or by a remote control system.  Honeywell Evo Home has a system that can accommodate the remote control of up to twelve wireless TRV’s through its dedicated software system and hardware. A broadband connection is required.

A system called Heat Genius works in a similar fashion to Honeywell Evo Home, but has the extra option of fitting motion sensors in individual rooms and areas. This allows the system to learn about the habits of the house occupants and predict energy requirements based on this learning.

The system also has adequate provision for build and add on technology as and when it becomes available. Installing a complete Heat Genius package in an average three-bedroom property with seven radiators would cost around £800 including the individual room sensors, the TRVs and the Heat Genius Hub.

The efficiencies and controls afforded by installing the components necessary to produce effective zoning are only part of the practical tasks associated with energy saving. Much of the efficiencies these systems deliver are dependent on the energy usage and awareness of the house occupants. Without a concerted effort to minimise heat loss, use energy with efficiency in mind and learn from the limitations of the installed systems, installing technology without interacting with it is a futile waste of time and money.

Where technology and adaptable human behaviour co-operate, major savings in energy and costs can be readily achieved.

Micro-bore Pipes for Central Heating Systems

Back in the 1970’s, micro-bore pipes were the revolutionary plumbing material for central heating systems. Copper pipe of between 8 mm and 10 mm was available on rolls and flexible enough to be gently bent by hand without the need for joints and soldering. New developments in manufacturing processes meant that micro-bore plastic pipes were now available that were durable and resilient enough to cope with high temperatures and pressure.

The simplicity of installation meant that installing the pipe-work for a central heating system could be regarded as a DIY task and the home owner could save a small fortune by not hiring a plumber. Professional installations could also be completed in a fraction of the time and at a considerably lower cost. Floorboards no longer needed to be lifted or notches cut into joists to accommodate pipe-work and the work was accomplished quickly avoiding all the previous domestic upheaval.

However, the systems were often incompetently plumbed, sometimes with little regard for boiler output capabilities or radiator output ratings. Micro-bore copper pipes were often kinked instead of being carefully manipulated to achieve curves. Consequently problems occurred which tended to tarnish micro-bore systems.

Keen to jump on the bandwagon of condemnation were the old school plumbers. 15 mm and above diameter copper tubing had long been associated with artisan plumbing practices. The skills that were a feature of the tradesman’s craft were being undermined by the simplicity and flexibility of small-bore copper and plastic pipes. As such, plumbing with such materials was often seen as inferior and cheap.

Never the less, many original micro-bore installations are still operating very effectively today and their owners swear by them for reliability and absence of any, or only minimal maintenance requirements.

The recent economic situation coupled with a growing awareness of environmental issues has seen a renewed interest in micro-bore pipe-work. The cost of copper has soared, along with the cost of other metals on the global market and as a result, entirely copper installations are expensive projects to undertake. The time required to install most copper heating networks is considerable. Time spent cutting and bending material and soldering, brazing or fitting compression joints adds to the cost installations. Not surprisingly, installers are looking at ways to reduce cost and remain competitive.

Micro-bore systems can be used for open or pressurised central heating systems that use a two-pipe flow and return convention.

Micro-bore heating systems can utilise the fact that very little water needs to be present in the system compared with conventional pipe-work. As a result, less boiler heat is required to heat the volume of circulating fluid and a smaller capacity boiler can be installed. The important considerations to observe are the distance of the radiators from the manifold and the output ratings of each radiator.

The pipe-work from the boiler to the manifold is generally 22 mm. Although it is better to place the manifold near to the boiler to save on 22 mm pipe, it is not imperative to do so. Either 8 mm or 10 mm pipe can run from the manifold to each radiator as a flow and a return, depending on requirements.

The length of pipe-work to each radiator from the manifold should be kept below 5 metres. Each radiator must be correctly balanced to provide an 11 degree C drop over its surface from the inlet to the return pipe. Some radiators may incorporate a double valve to accommodate both inlet and return feeds, which also economises on pipe-work.

It is general practice with micro-bore systems to run plastic pipe-work, usually Hep20, below the flooring and then revert to copper where the pipe becomes visibly attached to the radiator. Not only is this more aesthetically pleasing, it also acts to provide more durable pipe-work where unprotected exposure could lead to damage by children’s toys or by other knocks and bumps.

Because micro-bore pipes have less surface area, heat loss from the pipes is reduced. Avoiding joints, which might otherwise impede the smooth flow of central heating fluid, by gently curving the pipes improves flow rates of circulating fluids, but the system pump must be capable of supplying adequate force to compensate for the narrow diameter of the micro-bore pipes. The velocity of the pumped water must remain above 0.3 metres/second.

Because of their diameter, micro-bore central heating installations do require a little more consideration. Although there is no direct evidence to suggest that they are any more prone to blockages than conventional systems, it is advisable to maintain good system management and maintenance procedures.

Rather than advisory or good practice, the use of a suitable inhibitor is a must, as is regular system flushing. Flushing should be undertaken by a qualified and competent engineer who is accustomed to working on micro-bore systems. In hard water areas, the use of a water softener will guard against lime-scale formation, which if anything is more of a problem in micro-bore pipes.

Contrary to some advice, it is not advisable to bury micro-bore pipes for central heating systems within plaster or below concrete screeds. Although micro-bore pipes are used for under-floor heating, the temperature of water destined for central heating is considerably greater. Expansion of buried hot central heating water pipes will cause concrete or plaster to crack.

Micro-bore heating systems do require a little more consideration during the planning stages to ensure all operating requirements are met, but once installed there is no reason why the system should give any less performance or working life expectancy over conventional systems. On the contrary, a micro-bore system actually removes some of the problems that seem to blight larger bore installations.





Alternatives to Copper Pipe for Central Heating Installations

A few weeks ago, when I was considering installing a wet central heating system in a property I had bought to let, I asked our local plumber to quote a price. Once I had recovered from the shock, I asked him whether such a vast amount of expensive copper piping was actually necessary. Was there not an alternative?

“Copper’s proper” was his affronted response.

This quite naturally got me thinking about the alternatives to using copper in such circumstances. I was quite aware that such products existed and were often used, although my direct experience had been limited to the use of UPVC plastics for wastewater disposal.

I had also once taken a camping holiday with the family where the site water supply was routed to stand pipes through black alkathene tubing. I can distinctly remember the unpleasant after taste associated with not allowing the water to run for an appreciable time before collecting it.

In the past, plastics and their derivatives have come under much scrutiny, particularly where contact with them via food and drink has raised doubts about their safety.  Phthalates and other toxic components in PVC type products are known to migrate into materials that come into contact with them. Fears about the carcinogenic nature of the chemicals required for the manufacture of such plastics have raised doubts about their safety and the long term effects of the products on the environment has become a sensitive issue.

But potable water for drinking is a different consideration to that of wet central heating fluids and although I can understand that certain plastics may under some conditions release toxic materials into the atmosphere, I am sure that there must be alternatives to copper that are suitable for domestic heating use.

PVC, I discovered, is not suitable for use with hot water so that has to be ruled out.

Galvanised pipe, a zinc coated steel or iron pipe, requires so much cutting and threading that combined with its price, the cost of labour for installation could make it more expensive than copper.

CPVC can withstand temperatures up to 180 degrees and can accommodate push fittings like Sharkbite, making installation a straightforward procedure; however, the use of glues and solvents for some joint fittings tends to ring alarm bells for me in respect of long-term resistance to leaking.

Where CPVC pipe-work has required jointing with solvents and glues, the long-term effectiveness of the joints has become compromised by changes in the molecular structure of the bonding materials. Expansion and contraction of these types of pipe can weaken joint bonds, as can vibration where pipes have not been sufficiently supported.

Some plastic type piping introduced in the past, has been found to develop problems with degradation through exposure to sunlight UV and chemical pollutants in the air. Both rigid and flexible plastic pipes have developed a tendency to become brittle.

There are some plumbers using HEP20 barrier pipe for central heating installations. This type of plastic pipe incorporates a barrier that prevents air from penetrating through the wall of the pipe and entering the water system. This helps to reduce the effect of corrosion upon metal components within the system.  The barrier also acts as a good insulator, preventing heat loss between boiler and radiator. This type of pipe is cheaper than copper, is easy to cut and fit and when installed correctly is quite durable.

XIPEI or PEX as it is generally called is a versatile product often used in domestic plumbing installations. Its acronym stands for Cross-Linked High-Density Polyethylene. The product has been around since the 1970s but is becoming the material of choice in new homes. PEX does not require any glues and solvents, but does require dedicated fittings and special tools for making secure, watertight joints. The material is flexible for ease of installation and can be gently manipulated under floorboards and around corners. Bearing in mind that copper must be used for at least the first meter of piping leaving and returning to the boiler, PEX can be used for pipe lengths that are hidden from sight, coupling to copper or steel fittings above floorboards etc.

The material can be purchased on reels for cutting to required lengths. It is also available in colours suitable for colour coding, which is ideal for differentiating between hot and cold water supplies.

PEX is lightweight and durable, but requires adequate support when fitted. It is also a stable material and can withstand a variety of environmental conditions that could prove problematic for other materials, including copper. As a result, PEX material carries a long guarantee against defects.

Because a number of companies produce products made of PEX, it can be found that fittings and components vary. It is important to ensure that fittings are compatible especially when joining the material.

So. There are materials that can replace copper for central heating installations.

The main problem with copper is the volatile metals markets that can see prices fluctuate alarmingly. Currently copper and other metal prices are high. This volatility makes copper unattractive to some plumbers due to the reduced profit margins that can occur. Plastics, on the other hand are relatively cheap and price-stable making them attractive to plumbers. The speed and efficiency with which they can be installed reduces the cost of installation for plumbers, but not necessarily for the customer.

There can be no doubt that where plumbing has to be visible, copper carries a particularly aesthetic quality that can never be replaced by functional plastic. It is also fair to say that most plumbers will view copper as being the material of quality and artisanship.

Plastics are ideal for DIY where plumbing skills are perhaps limited, but as with all plumbing, ease and efficiency are not necessarily the essence of reliable and durable installations.

However, because I am aware that a copper installation will reflect on the desirability of my buy to let property should I come to sell it, and that my buildings insurance company does not take a positive view when it comes to alternative heating plumbing materials, “copper” certainly seems “proper.”

Drain Cock Not Working or Blocked


You have planned to drain the central heating system. You have turned off the boiler and water supply. The system has cooled down. You have released pressure, particularly if the system is pressurised. You have opened radiator bleed valves. You have located the central heating system drain cock and attached a hosepipe to it to facilitate drainage. You have even secured the hosepipe with a jubilee clip as an added precaution. What could go wrong?

You try to turn the drain cock spindle with an adjustable spanner. But it will not move.

So what can you do?

Well, depending on the time of year and the location of the drain cock there could be a possibility that it is frozen. Central heating drain cocks are often located outside for a variety of reasons; one being that central heating fluid can permanently stain any material it comes into contact with. Installing a drain cock outside the house prevents that problem, but without adequate insulation renders it liable to freezing, and even splitting in severe frosts. A frozen drain cock can be freed by applying a heat source.

All drain cocks are prone to seizing due to infrequency of operation.

If the drain cock is located internally, the application of a releasing fluid, such as WD40 could free a seized mechanism. It may take a few minutes for the fluid to penetrate sufficiently to be effective. Take care when trying to turn a stubborn spindle, it can snap off.

Another big danger in trying to turn a seized drain cock spindle with grips, or an unsuitable spanner, is the sheering away of the square spindle top. Often drain cocks are situated in areas where there is little room to manoeuvre spanners and grips. Once sheered, the drain cock becomes almost impossible to operate compounding the problem. It is possible to purchase a dedicated tool, which is ideal for opening and closing drain cocks in awkward places.

Sometimes a drain cock spindle will appear to turn freely, but no central heating fluid flows out of the system. Assuming that radiator bleed valves are open and that no internal vacuum is preventing fluid from flowing, it is probable that the drain cock is blocked. This can be caused by a build up of sludge blocking the drain cock, or the detachment of the drain cock washer from the spindle. Occasionally, the washer can adhere to its seating in the valve, particularly if it has been over-tightened and can detach from the spindle when it is operated.

It is not unheard of for an incompetent plumber to melt the washer, sealing it in the closed position when soldering a new drain cock onto pipe-work. Of course, this only comes to light at a later date when it becomes necessary to operate the drain cock.

Where sediment is suspected of causing a restriction to flow through a drain cock, it may be possible to clear the blockage by delivering a reverse flow of water into the system through the hosepipe attached to a mains supply and onto the drain cock. This should be done in short bursts, removing the hosepipe from the mains tap each time to check whether flow has started.

Where a detached washer is suspected, it is possible to insert a screwdriver into the drain cock outlet and attempt to dislodge the washer. Of course, precautions must be taken to accommodate a sudden flow of central heating fluid, which will occur once the washer is dislodged. Plenty of towels and absorbent material will soak up fluid spillage whilst a hosepipe is hurriedly attached to the drain cock spout.

Naturally, the system cannot be refilled until a new washer is fitted or the old drain cock is removed and a new one fitted. Fitting a new washer is a simple task as long as a suitable replacement is sourced. Stripping down the drain cock is a simple procedure. A new washer can be pushed onto the jumper and the body re-assembled. Always take the old washer along to suppliers to get an identical match. Washers should be replaced after several years to prevent fluid dripping due to deterioration.

Where there is a sufficient leg of pipe-work leading to a seized drain cock, it is possible to drain a central heating system by installing a temporary self-cutting drain off tap or a self cutting washing machine valve. However, it would be best to remove these and fit a new piece of pipe with a functioning drain cock prior to re-filling the system.

Where no drain cock can be found, it is possible to drain a central heating system by finding the lowest and smallest radiator in the system. Find the plug usually located at the top of the radiator. Turn off the wheel head and lock shield valves. It is then possible to remove the plug and by inserting a half-inch fitting, attach a hosepipe to the end of it. Opening the wheel head and lock shield valves will allow most of the central heating fluid to be drained. The remaining fluid can be drained by detaching the radiator at the bottom return flow and catching the fluid in a suitably sized container. Where possible this method should be avoided and only used as a last resort due to the inevitable large quantity of central heating fluid spillage.

Many problems with drain cock operation can be prevented by frequent operation and adequate insulation against frost. This applies to drain cocks fitted to any domestic system. Never over tighten a drain cock.





Automatic Air Vents

There is nothing more disturbing than the banging and gurgling noises that can issue from boilers and the hot water systems they supply. Often the noise is caused by air in the system. This can be air that has entered the system during repair or maintenance procedures, or air that is entering the system regularly and causing unacceptable operating noises. Regular addition of air into the system can be indicative of a general fault in the design, layout or operation of the system.

Automatic air vents (AAV’s) are handy devices that can be fitted to automatically expel air from hot water systems.

Most boilers incorporate some form of AAV, often concealed below the external casing, and therefore out of reach of any DIY or unregistered installer. However, these devices may not remove air trapped within the wider hot water system.

In these situations, the fitting of an AAV in the circulatory network may alleviate the effects of the problem. Bungalows and single storey dwellings, where insufficient head of pressure can sometimes allow air to enter into the hot water system, will benefit considerably from the fitting of an AAV.

Although a number of companies manufacture domestic AAV’s, the general principle of valve operation for inline valves is much the same. The valve is installed into the hot water system at the highest point.

This highest point must be on the positive sides of any water pump. This can be identified by locating the pump and establishing the direction of flow. This will be indicated by an arrow, usually cast into the pump housing.

Fitting an AAV on the opposite side of the pumped flow can result in air being drawn into the system by creating reverse pressure in the valve. This will naturally compound the problem rather than alleviate it.

There is often a part of the system that crosses from one point to another by virtue of an incline followed by a decline in the pipes horizontal plane. It is at the apex of points like this that air is likely to congregate and in some cases severely restrict or prevent water flow.

This is an ideal location for the installation of an AAV. To maximise operation, the AAV should be plumbed into the system by inserting a ‘T’ piece joint into the main pipe-work and providing a few inches of vertical pipe between the valve and the main pipeline. This vertical pipe will ensure that a suitable pressure of air builds up to push water back down this pipe and cause the valve to function efficiently.

The valves contain a float mechanism that allows air to be expelled. The float contains air that provides buoyancy allowing the float to sit on top of the water surface contained with it in a chamber. Because air will collect in the highest point of a system, air enters the chamber and displaces the water. This causes the water level in the chamber, and the float, to fall. As the float drops, its attached mechanism opens a valve to release the air. As the air disperses, the water level rises in the chamber again, raising the float and closing the valve.

The valve also incorporates a closure nut at the external outlet of the air release valve. This can be manually operated to close the valve in the event of it becoming faulty and starting to expel hot water. This can be caused by sticking float or valve seal. Routinely giving the valve a sharp tap with a hammer will help to prevent an infrequently operating valve from sticking.

Although many AAV’s claim to have an inbuilt sealing device to close off the circuit and allow the valve to be removed for servicing, it would most unwise to rely on it. It is better to turn-off the boiler and pumps and release any pressure prior to removing an inline AAV.

In a central heating system, trapped air in radiators is usually released through the bleed valve located on each radiator. A build up of air, and other gases, can become a frequent occurrence on some central heating systems leading to inefficient operation. Radiators are often cold at the top and air in the system can accelerate corrosion in the radiators dramatically reducing their lifespan. This is particularly so where inhibitor has not been added regularly and central heating maintenance schedules have been disregarded.

Where the frequent necessity of radiator bleeding has become onerous, small AAV’s, particularly designed for individual radiators can be fitted.

These devices can be readily purchased from most DIY and plumbing merchants, usually for around ten pounds.

Fitting these devices is generally straightforward. With the heating and pumps turned off, and the system cool enough to work on, each radiator should be turned off at the inlet valve and the lock-shield valve. The lock-shield valve is located at the opposite end of the radiator to the inlet valve and is usually operated by removing the white cap and turning the exposed spindle with a spanner or set of grips.

Before attempting to fit the device, any pressure in the radiator must be released by operating the radiator bleed valve.

The AAV can be installed by removing the bleed valve and directly replacing it. Many people prefer to leave the bleed valve installed and simply attach the AAV by removing the locking nut at the opposite end of the radiator to the bleed valve and fitting the AAV there. Because many radiator AAV’s contain check valves to prevent air being drawn into the system, leaving the bleed valve in place allows for easy operation if the system requires draining.

Once installed, the system and pumps can be turned back on and a hissing sound should issue from the AAV indicating that trapped air is being expelled. Once the air is removed, the AAV should automatically close to prevent central heating fluid escaping.

Before working on radiators, sufficient precautions must be taken to catch any spills of central heating fluids, which can irreversibly stain any materials they come into contact with.

If, after fitting an AAV on a radiator, air remains in the radiator, it may be due to too much air preventing the AAV operating at all. This can be remedied by turning off the boiler and pumps and removing the AAV. Then, by turning on the pumps, water will fill the radiator expelling any air. As soon as water dribbles from the fitting point, the AAV must be quickly replaced.

Fitting an AAV will remove air from a hot water system. Re-occurring problems with air in the system should be investigated to determine the cause.

Sometimes the water supply simply contains too much air when it is supplied to the property. This can often be caused by extensive maintenance work carried out by the utility company and may be a temporary but irritating situation.

Excessive quantities of air in the system may indicate a potentially serious problem with the boiler or the water supply and professional help should be obtained to prevent damage to the system.


How to Hang a Radiator

Perhaps you have decided to upgrade your central heating system with new, more efficient radiators. Maybe you have decided that you need to add another radiator to the system. It could be that you have had a power flush and been informed that one or more radiators are irreversibly clogged up with sludge and need to be replaced. Alternatively, it could be that you have just had a thorough re-decorate of your property and the next job is to re-install the radiators.

Whichever one, you are going to have to fix a radiator to a wall.

You could get a quote from a trades-person. If you do, you can expect to pay a considerable sum. Not because it is a particularly specialised task. The cost lies mainly in the trades-persons’ time.

However, even with the minimal amount of D.I.Y. knowledge and experience, the task of hanging a radiator is a quite straightforward procedure.

Let us assume that the central heating system, or radiator section, has been isolated and drained.

If you are re-hanging a radiator after decoration, simply attach the radiator onto the existing brackets and re-plumb it back onto the system.

If you are replacing a radiator with one having similar dimensions, you may be fortunate to find that the new radiator fits onto the existing brackets, if not, read on.

So. You have made the decision to either add a new radiator to the system or install a replacement. You’ve checked the boiler capacity to ensure that any addition will not adversely affect the system output, and considered the destination room’s British Thermal Units (BTU) requirements by calculating the room’s cubic capacity in feet (L x W x H) and multiplying that figure by four. The new radiator should have a corresponding BTU output rating.

On a new radiator, this will be indicated on the back.

Now you will need to decide where to locate the radiator within the room. Conventionally, a radiator is usually positioned in a feature, such as an alcove or below a window. If you are intending to plumb into existing heating pipe-work you will need to consider the layout of the pipe network, which may be concealed beneath floorboards.

It is important to establish the construction material of the wall upon which the radiator brackets will be fixed. For brick and plaster, concrete or stone, conventional screws and wall plugs will suffice. Plasterboard will require special expanding rosette screws, or for large radiators, batons secured to the plasterboard to distribute the weight. If your room has dry-lined walls you will need to cut through the interior lining and secure bracket-supporting batons to the internal supporting wall.

Bearing these points in mind you will be able to proceed and position the radiator support brackets.

Lay the radiator on the floor with the back facing upwards. It is wise to protect carpets or wooden floors by laying the radiator on cloths or cardboard.

To fit the radiator centrally, measure the length of the wall at a height of around two feet. Establish and mark the wall centre and then, using a spirit level, draw a vertical line from the skirting board upwards bisecting the horizontal centre.

Most radiators are fitted to sit four to six inches above floor level; however, if other radiators are already installed on the system, it is advisable to maintain the same height across the system. If you are replacing a radiator, bear in mind the height of the existing plumbing facility.

Mark this height on the wall.

Turn your attention to the radiator. Take one of the radiator brackets and slot it into the radiator fixing slots. Now measure from the base of the radiator to the base of the bracket.

Take that measurement and transfer it to the previously made radiator base height mark, and working upwards, make a mark establishing the level for the base of the radiator bracket.

Using a spirit level, mark a long horizontal line across the bracket level mark.

This line will be used to position the height for the bracket.

Now return to the radiator, and removing the bracket, measure the distance on the radiator between the centres of the two bottom hanging slots.

Divide this measurement by two and return to the wall markings.

On the horizontal bracket line, transfer a one-half measurement along that line commencing from the vertical line to both the left and then the right, marking both.

At both these marks use a spirit level and draw a one-foot vertical line bisecting the marks.

Now take each bracket in turn and using the point of the bisecting lines, align the bracket. Mark through each bracket screw fixing holes onto the wall.

Drill and plug the holes and finally attach the brackets.

Lift the radiator onto the brackets; it is sometimes easier to tilt the radiator forward slightly. When the radiator is secure, place a spirit level across the top of the radiator. You should be able to congratulate yourself.

You will be able to lift the radiator off the brackets and decide which side to fit the appropriate input and lock shield valves. This will depend of the direction of flow of the central heating system.

The radiator will then be ready to plumb.

Do bear in mind that if you are installing a radiator or a central heating towel radiator in a bathroom, the radiator should be earth bonded for safety

Preparing Your Heating System for Winter


Now that the day light hours are shortening and the leaves on the trees starting to fall, home-owners’ thoughts naturally turn to the prospect of re-starting the central heating system.

The temptation can often be to delay the switch on for as long as possible to save money. Some home-owners may consider waiting until a good early morning frost makes the prospect of getting out of a warm bed so un-appealing that turning on the heating remains the only option.

However, leaving the central heating switch-on until winter starts to bite can leave home-owners vulnerable to unexpected problems with the system at a time when the heating is needed the most.

There is much to recommend planning a schedule of maintenance and service procedures well in advance of the first cold snap.

Although not obligatory for home-owners, an annual boiler service may be a condition of a boiler warranty agreement.  Autumn is good time to get the Gas Safe registered engineer out to service and check over the boiler.

Some boiler checks can be undertaken regularly by the householder, such as checking for a crisp blue pilot light if the boiler has one. Maintaining an adequate boiler operating pressure of around 1.5 bar can be achieved by activating the valves at the base of the boiler. It is important to turn these valves off again once the pressure dial on the boiler reads the correct operating pressure.

Starting up the central heating well before the first frosts are expected will help to identify other problems that may appear after the summer of inactivity.

Thermostats and timers will need re-setting to account for winter conditions.

Electrical components may need turning on at isolation switches.

Occasionally pumps that have been inactive for a period may need the gentle persuasion of a sharp tap with a hammer to dislodge resistance caused by debris.

During first operation, radiators should be carefully checked by running a hand over them. Radiators that are cold at the top may need bleeding. Radiators that feel cold to the touch at the base may have developed an accumulation of sludge and debris.

When the central heating is not operating during the summer months, particles normally held in suspension in circulating radiator fluids, settle out and congregate at the bottom of pumps, pipes and radiators. These generally need removing by power flushing. Regular power flushing will help to prevent this seasonal problem.

Now is also a good time to check the mains water stopcock to ensure that if a winter water emergency arises, the stopcock is free and easy to operate.

Checking the insulation on an external condensate draining pipe of a gas condensing boiler is an absolute necessity. Any deteriorated insulation lagging should be replaced. A frozen condensate pipe will prevent a condensing boiler from operating.

Around the home, other early winter precautionary checks can prevent problems during the colder months.

One of the benefits of good home insulation is that domestic accommodation has benefited by preventing warm air from escaping via drafts and by conduction through walls, floors and roof spaces.

This, however, can create other problems that now need addressing.

Many water service pipes run up into the loft spaces to facilitate good gravity feed to outlets. These pipes are often located above the generous loft insulation layer and if not properly insulated they are vulnerable to frost damage. A burst pipe in the loft can cause horrendous damage to property and contents. The lagging on these pipes should be checked annually, as should the lagging and insulating jackets on water storage tanks that may also be located in the loft.

With home insulation comes a problem with condensation. Autumn is a good time to check that external air vents are not obstructed with leaves and other debris. Air vents in bathrooms should be checked for blocked meshes. Some windows have mesh ventilation panels, or trickle vents, incorporated into the frames. These panels should be in the open position for winter and the mesh clear of debris.

External drain pipe-work that facilitates drainage from washing machines and dishwashers should be checked for blockages and insulated. Blockages in theses pipes caused by frost or debris can result in the appliances pumping drainage water into their surroundings causing considerable water damage.

External taps and water pipe-work should be either drained if they are not likely to be used, or sufficiently insulated against frost.

Although installing double-glazing is a good insulation practice, some period properties are unable to install it due to listing or other practical considerations. In any property without double-glazing, thick heavy curtains, specifically made for winter use can replace light, airy summer ones. Such winter curtains are very efficient at insulating cold windows and reducing cold drafts.

Do not forget to check the working operation of smoke and carbon monoxide detectors. Fitting new batteries annually where required and replacing the appliances in line with the manufacturer’s recommendations, usually every five to ten years.

It can be a good idea to keep a list of emergency plumbing and heating contact telephone numbers at hand, perhaps pinned to the kitchen wall.

It is also good practice to ensure an emergency back-up of torches, electric heating appliances, tinned foodstuffs and a fully charged mobile phone are available should the need arise.

By adopting a pre-winter routine check and review of precautions, and the early trial running of appliances, the household can eliminate most of the potential problems before they occur.

This can prevent considerable distress and damage from emergency situations that could easily be avoided.





Fixing a Leaking Radiator



A leaking radiator may create a myriad of problems and can often be the cause of boiler operating inefficiencies and system pressure issues.

Inconspicuous leaks from radiators and fittings can cause damage to carpets and floorboards and create damp and mould problems in surrounding areas.

Where tiny leaks are suspected or observed, a sealant treatment can be purchased which may provide a temporary solution to the problem.

The sealant is a solution which is added to an open vented central heating system expansion and feeder tank in the loft, or into a sealed system via the boiler loop or a radiator.

Some sealant products are not suitable for use in sealed or pressurised systems so care should be taken to ensure that the appropriate treatment is purchased.

It should also be kept in mind that some boiler warranties can be invalidated by the addition of treatments that are not specifically approved by the boiler manufacturer.

Leaks in the body of the radiator itself cannot be effectively repaired and the only solution to a leaking radiator is its replacement.

Where inhibitors have not been added to a central heating system, the radiators become particularly vulnerable to corrosion. Corrosion can be caused by many chemical processes but electromagnetic fields can cause pitting within the radiator shell. This is because modern radiators are constructed from pressed steel. This is connected to the central heating system by copper and brass fittings. The oxygen in the central heating water creates an electromagnetic field between the two metals causing the steel to corrode.

Radiators supplied by inhibitor maintained systems can last for many years. Where inhibitor is excluded, the radiators could need replacing completely every five to eight years.

On pipe-work and fittings supplying the radiator, a piece of tissue can be used to try to locate a leak. First, dry the area thoroughly with an absorbent cloth. The tissue should then be carefully dabbed onto to the suspect areas and where the tissue comes away damp the location can be identified.

Care should be taken to identify correctly where the water is coming from. Occasionally on a radiator valve, water may pool on the union nut directing attention to a potential leak from the coupling. However, the actual leak may stem from the radiator valve itself.

Where a leak is suspected of coming from the radiator valve, the screw on top of the tap should removed allowing the tap to be lifted off. This will reveal the central spindle and the valve housing. The valve housing itself is sealed and is usually not repairable or replaceable without draining down the system. At the top of the valve housing is a hexagonal nut, which should be removed.

At this point if water has been leaking up the spindle its presence will be evident.

It is possible to re-pack the area around the failed internal washer by gently pushing a length of rolled up PTFE tape around the spindle and then poking it down into the base with a bradawl.

The amount required is judged by trial and error but it must not impede the ability of replacing the hexagonal nut. The replaced nut must not be tightened too much or it will make the operation of the spindle and tap difficult.

Modern central heating systems tend to use compression fittings to join the heating flow and return pipes to the radiator. If one of these fittings is leaking, it may be possible to remedy it by tightening the attachment nut with a spanner carefully by a quarter of a turn. This will compress old PTFE tape and the internal olive slightly and hopefully remedy the problem.

If that procedure fails to prevent the leak, it will be necessary to drain down the radiator or the entire system if the radiator cannot be isolated.

When working on areas where radiator fluids may spill out it essential to protect carpets and floorings from contamination. Usually the residual fluids contain the sludge material, which will permanently stain anything it comes into contact with. It is advisable to have suitable containers on hand ready to collect any unexpected gushes of radiator fluids, particularly where the opening of the bleed valve may have been omitted.

The suspect compression fitting can then be dismantled, cleaned and the old olive removed and replaced. If the old olive stubbornly refuses to be prised from the pipe-work, it can be carefully removed with a junior hacksaw by cutting at a suitable angle.

When attaching the new olive it is good practice to smear some silicon sealant or PTFE tape around the olive prior to final fixing.

The threaded parts of the pipe-work should be thoroughly cleaned and PTFE tape wrapped around the pipe thread. The fitting can be re-attached to the radiator and the system re-filled and operated.

Occasionally, a leak may occur due to failed ‘O’ rings in the lock shield valve. These can be replaced by accessing the internal spindle.

If the central heating system drain valve is leaking, the area will need to be isolated or the system drained down. The spindle can then be removed with a spanner and the washer at the end replaced. The replacement washer should be made of fibre. Rubber washers are prone to deterioration due to extensive contact with the hot central heating fluids.

When repairs have been completed, the system can be re-filled, not forgetting to include inhibitor at the required concentration. Radiators will need bleeding to release air in the system.

After any plumbing and maintenance operation, the system should be monitored for any further leaks or potential problems.



Choosing the Right Radiator

Domestic wet central heating radiators are moving up in the home decor market, from the unobtrusive to the chic. Gone is the association with the community institution and the low profile room fitting. The functional bland heat emitters are becoming sophisticated energy efficient focal points, adding character and charm to their surroundings. They have become statements about their owner’s lifestyle, preferences and ambitions.

If that has you looking at your old existing central heating radiators and thinking it might be time for an upgrade, you are probably correct. However, if you have recently installed the latest conventional system you might now be wishing you had considered a more futuristic and designer focused approach.

When it comes to replacing radiators, you are no longer restricted to adopting a like for like replacement. There is now an array of stylish radiators in a wide variety of technical specifications, materials and types of construction.

For new build installations, building conversions and renovations, modern and period, the choice available is wide and growing.

So where do you start when it comes to choosing radiators for new or existing systems. It can be an interesting exercise when looking at upgrading an existing system to discover whether the boiler currently satisfies the demand required by the radiators to efficiently heat each room’s area.

The output of a radiator is rated in BTU’s/hr. and kWh. This information is usually found on the back of a radiator. For maximum efficiency, the radiator’s output should match the room’s heat requirement.

In order to make a calculation to determine the required output from a radiator, the area of the room should be calculated in square feet. As a rough indication of requirement, multiply this figure by four to convert to BTUs. To get a more reliable figure, other information like the area and number of windows, the number of external walls, the rooms above and the floor composition are required.

There are free online calculators that can process this information and provide a comprehensive BTU’s/hr. and kWh requirement.

Once this calculation for all the rooms has been established it should be checked against the boiler’s output rating to ensure that the boiler has been, and can continue providing, the required energy to satisfy the radiator and room requirements.  In most cases, it will be found that boiler capacity exceeds the central heating requirements.

The same room calculations are required to determine the whole central heating system requirements in new build and full installations.

When purchasing new radiators it is important to establish whether they are to be installed into an open or sealed central heating system.

Armed with this information, prospective radiator purchasers should consider style and efficiency. Modern panel radiators are more of an efficient convection device than their predecessors.  They can be described as Single Panel, Double Panel and Double Convector Radiators. They incorporate fins that allow air to circulate through them. This creates convection currents that heat a room more efficiently. The front panel also radiates heat. The type and number required will depend on the size of the room and its heating energy requirement.

Column Radiators, as the name suggests are based on the traditional model of columns of radiator pipes. Original old column radiators can be purchased to give a genuine nostalgic effect or for the enhancement of period surroundings, however these must be fully restored and pressure checked to ensure that they are robust enough for modern systems.

Designer radiators have become vogue for modern homes. In order to compliment the cutting edge style of technology and innovation found in sophisticated room decor, these radiators incorporate sleek aesthetic design with stunning visual impact. With an abundance of shapes, colours and sizes available, they require some creative forethought to establish how they might work with your interior design ideas. Increasingly they are becoming custom finished to a customer’s personal requirement.

When it comes to the materials used in the construction of radiators there is now considerable choice available. Good old cast iron is great for creating period ambience in large rooms. Traditionally the construction material for column radiators it continues to radiate heat long after the central heating is turned off. The drawback with cast iron is its weight. It does require a strong floor to provide adequate support.

Stainless steel is another consideration. This prestigious material has a number of desirable properties.  Stainless steel does not rust, however it is important that the correct grade of stainless steel is used in radiator manufacture. There are some grades of stainless steel that are not suitable for radiators. It is important to choose carefully as cheaper products may fail to deliver long-term durability. Stainless steel can offer some attractive finishes which are very easy to clean.

Aluminium radiators are lightweight super-conductors. They are extremely responsive to temperature, which means they heat up and cool down rapidly. This material is perfect for modern homes where space can be limited. Aluminium is non-corrosive and, because of its versatility, can accommodate a narrow gauge of internal heating fluid containment, which aids energy efficiency. Aluminium radiators come in a range of colours and finishes and can be selected to harmonise with the room’s internal decor. When it comes to function, attractiveness and economy aluminium is often the material of choice.

Metals continue to provide the mainstream materials for domestic radiators.

When mixing different radiator metals within a central heating system consideration should be given to the potential for acceleration of corrosion. It would be appropriate to seek further professional advice on the matter.

Emerging onto the radiator market are glass and stone models, which are extremely energy efficient. These materials are superb for incorporating artwork and sculpture into their designs.

Choosing the right radiator is becoming a decision based on much more than functionality.

As demand for more efficient and stylish radiators continues to increase, innovative materials and designs are changing perspectives on the solely utility perception of domestic central heating systems. Sleek design, high-energy efficiency and improved durability in radiators are the current focus. These attributes coupled with high-tech gas boilers and futuristic control systems will ensure that homeowners can look forward to central heating systems that deliver on style and performance.