DIY How To

DIY Projects - Fit radiator valves

Modern central heating systems need to be maintained to keep there efficiency and reliability. Boilers and radiators can have their life span reduced to less than ten years if proper maintenance and servicing is not carried out.

Safety AdviceAny maintenance that involves removing or refitting components on a gas boiler must be carried out by a CORGI registered engineer.



Corrosion can be caused from a chemical reaction between the various metals used throughout the system and the water in the system. Rust corrodes the steel components in the system, this is most noticeable with the radiators. Rusting occurs more or less as soon as the system is filled with water, but the presence of air in the system dramatically speeds up the rusting process. Having to regularly bleed the radiators shows that air is getting into the system.

Check your System

Drain a pint of water from the system as a sample and check the colour.

  • A dirty grey colour is normal.
  • A dirty black colour indicates some sludge.
  • A rusty colour indicates some corrosion.

If there is any indication of sludge or corrosion, a corrosion inhibitor needs adding. If the system is more than six months old make sure the system is de-scaled first. The corrosion inhibitor can be added to the system by turning off the boiler and pump and isolating the water supply to the feed and expansion tank.
Drain off the water until the tank is empty, add the inhibitor to the tank and restore the water supply, turn on the system and start the pump which will circulate the inhibitor through the system.

If the system is a number of years old it is better to flush the system through by draining and refilling repeatedly until the water runs clear. Once the water is clear the inhibitor can be added to the system on the final filling.

If there is no evidence of corrosion do a simple check to see if the system contains enough inhibitor. Drop a steel nail into the sample water and leave for a couple of days, if the nail starts to rust you will need to add some inhibitor.

Make sure the same inhibitor is used as any already present in the system, if you do not know what make of inhibitor is in the system, then drain and flush the system and refill adding the inhibitor.


Lime scale builds up on the inside of the boiler's heat exchanger which reduces the boilers efficiency and can cause the boiler to make a banging noise. If you live in an area where the water is hard the lime scale will build up quicker. To de-scale the system use a mild de-scaler which can be introduced via the feed and expansion tank. When the de-scaler has been added run the system continuously for a week with the boiler set to a high temperature, then drain and refill the system three or four times.

Some de-scalers need to be neutralized before an inhibitor can be added, check the manufacturer's instructions.

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