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.