What is Inhibitor, and How Do I Use It?


Water, albeit a rather good medium for the transportation and distribution of heat energy around the home, has the disadvantage of transporting additional and unwanted substances into and around your wet central heating system.
It will also react with metal by using oxygen molecules to create rust.

Take a look inside your kettle.

Chances are you’ll find a layer of lime scale firmly bonded to the element and gritty flakes layering the base.

The same thing can occur in your central heating system and be compounded by s other impurities, slowly creating a thick sludge.

Left untreated and with the central heating system un-maintained, over time these impurities and sludge build up causing serious reductions in the efficiency of the system and eventually considerable damage caused by blockages in the pipe-work and extra strain on the system pump.

The most effective way to avoid these problems is to add an inhibitor into the system.

An inhibitor is a solution containing biocides, anti-corrosion and anti-scaling chemicals. There are a number of proprietary brands that can be purchased from Do It Yourself outlets, but they all do much the same thing. A one litre container of inhibitor is usually enough to treat ten radiators.

Firstly, you will need to find out what type of central heating system you operate.

The main two types are open vented and sealed systems. If you are not sure which you have refer to your manufacturer’s guide.

If you have a sealed system, which is pressurised, I would suggest that you source additional or alternative advice as the procedure for adding the inhibitor can be a little more complex.

In an open vented system, the radiators are filled and kept topped up by a small header tank situated in the loft.

To begin with, firstly turn off the boiler heat supply. This is the gas, electric or solid fuel boiler, in the case of the latter, ensuring that the fire is completely out. Turn off the system pump.

Then enter the loft and locate the small supply header tank. Take care to distinguish the smaller tank from the larger domestic supply tank.

Either turn off the water supply to this smaller tank or securely tie up the ballcock to prevent the tank re-filling.

Once this is secured, leave the loft and look for the system drain tap which is usually near to the bottom of the boiler or the pipe leading from it.

You will need to secure a piece of hose pipe to the drain tap and feed this to an outside drain.

Open the drain tap with a spanner or pliers and allow the system to drain. This process can be improved by opening each radiator bleed valve to allow air into the system, starting at the top of the house and working down.

When the system appears to be drained, a good way of checking that this indeed is the case is to obtain the help of an assistant to watch the drain hose outlet. Go up into the loft and allow a few pints of water to flow into the system feed header tank. Your observer downstairs should notice the extra flow of water shortly afterwards.

If all is well, turn off the drain tap and remove the hose pipe.

On the odd chance that your observer saw no water, then try repeating the observation process. If this still is an issue, it is likely that there is a blockage in the system and further advice must be sought.

To refill the system, close the radiator bleed valves and return to the loft with the inhibitor.

Empty the litre of inhibitor into the system small header feed tank and turn the mains water supply back on or untie the ballcock.

You will now need to bleed the system through to remove any air trapped within the system. Start with the drain tap. Carefully open this whilst using a small vessel to catch any liquid that will be released. Then bleed the radiator valves starting at the bottom of the house and working up to the bedrooms and bathroom.

The central heating system can now be re-started.

It is a wise precaution to keep an eye on the system as it returns to proper functioning. You will also need to re bleed the radiators as any air left in the system expands with heat. This expansion may cause a bit of a knocking sound, but bleeding will correct this problem. Keep an eye open for leaks in the system and do ensure that the bleed valves are securely closed.

This procedure of draining the heating system should be done in line with the manufacturer’s recommendations, but at any time that it becomes necessary to drain the system, the addition of inhibitor when re-filling the system should be considered as standard practice.

Common Boiler Problems


Usually, the first sign of a boiler problem is a cold welcome. The copious hot water and the cosy domestic environment so easily taken for granted suddenly freezes into an arctic nightmare.

In most cases, these breakdowns occur when they are least expected or at the most inconvenient of times, for example in the middle of a gentle waking hot shower or when you have your infirm and elderly relatives staying with you.

In the midst of the ensuing panic, a cool and pragmatic approach can sometimes resolve the problem before incurring a costly unsocial visit from a heating engineer.

There are a few practical steps you can take to either solve the problems or at least eliminate them from a problem diagnosis.

If you have no heating whatsoever, check the digital display, if your boiler has one, to ensure it has an electrical supply. Occasionally a fuse spur switch that supplies electricity to the boiler is badly placed and the switch can be accidentally turned off. Failing that, the fuse in the spur might need changing.

If you have hot water, but no heating, check the room or radiator thermostat settings, particularly if they are within the reach of tiny hands.

If you have heating and no hot water check the thermostat on your hot water cylinder if your system incorporates one. If the thermostat setting seems correct, turn the setting up and listen for a click. Its absence may indicate a malfunction of the thermostat control.

Failing that, your system may have a motorised diverter valve close to the hot water cylinder. This diverts the boiler-generated hot water into the cistern heating coil. If the motor fails, there is usually a manual diverter lever on the side of the unit, which can be operated as temporary measure until a repair, or replacement can be arranged.

If you have a modern condensing boiler that refuses to operate, consider the weather. In freezing weather, unprotected external condensate drainage pipe-work can cause problems if it becomes blocked with frozen condensate. In this event, the boiler will close down completely until the frozen pipe-work is free draining. This can be achieved using kettles of hot water, but it can take some time.

If you have a vented or open system, a lack of domestic hot water can be caused by an air lock in the cistern inlet pipe. This is often created if the feeder and expansion tank in the loft runs dry, usually the fault of a sticking or damaged ball cock valve. Getting the water running into the feeder tank will resolve the problem.

If, having carried out these basic checks the problem has not been resolved, the next step is to address other possible causes, but these are likely to require attention from a heating engineer. However being able to supply an engineer with preliminary information can save considerable time and cost.

If you have a new boiler, a diagnostic function will display any error codes. These can be forwarded to the engineer who can then attend fully equipped to remedy the problem.

If your boiler is losing pressure, take a close look at your central heating system, particularly the valves for any sign of leakage. However, if your boiler is leaking considerable amounts of water, turn the mains water off at the stopcock and then run any taps to drain the water in the system safely.

Another fault to consider is a general thermostat issue. Thermostats can become less accurate and unreliable with age. Sometimes this can be rectified by giving them a good clean and recalibration by a heating engineer.

On older systems, pilot lights can pose a problem when they either refuse to light or are frequently extinguished. This can be due to a damaged thermocouple which may need replacing, or a broken air seal allowing draughts to extinguish the flame. In the absence of a functioning pilot light, or on a modern system an electronic spark, the boiler will not function. On some older systems the gas burners can be lit manually, but this is not to be recommended.

An unusual banging or hissing noise coming from the central heating radiators can be alarming, but is often caused by air trapped in the system. This can often be remedied by bleeding the radiators using a radiator key. Sometimes the same noises can be caused by lime scale deposits in the boiler or even low system pressure.

A broken central heating circulation pump may cause cold radiators all around the system, or in some cases due to the natural convection and circulation properties of hot water, hot radiators upstairs and cold radiators downstairs.

If your boiler is fitted with a flue fan, failure of this component is a likely problem after a couple of years of operation. Generally, the boiler will fail to start if this is the case. A failing flue fan will generate a noticeable difference in the usual operating noise of the boiler.

Overall, you can do much to minimise the risk of boiler failure problems by ensuring regular maintenance procedures are carried out and that your central heating system is robust enough to cope with the demands placed upon it. In the unfortunate situation where a boiler problem occurs, the ability to provide emergency heating and other domestic requirements with appliances operating on other fuels is something worth considering in advance.