Tackling central heating problems

Common Problems
If the central heating doesn't turn on, the most common cause on a gas boiler is that the pilot light has blown out. Check the maker's instructions and relight.

If the light is working, it may be that the thermostat is set too low or the timer isn't working. Check both and try again.

The overflow pipe is dripping...
The overflow pipe is the pipe that protrudes through the house wall or roof and allows water to escape if the water tank becomes too full. A dripping pipe is usually caused by a worn float valve washer or a damaged float valve.

Plumber's merchants will stock washers and new float valves. To replace, turn off the cold water supply to the feed and expansion tank in the loft. Lift up the tank cover and use a bucket to remove enough water to remove the valve and replace or repair.

There are leaks in the pipework...
Leaks in the pipework are easier to spot upstairs than on the ground floor, where water may drain away without damaging the structure of the house. Look out for dark patches on ceilings or damp flooring. A drop in the pressure of a combi-boiler system can also indicate water is leaking somewhere in the system.

If the leak is at a joint, turn off the central heating and tighten the joints with adjustable spanners or wrenches. Dry the joint and wrap some tissue around the pipe to check if there is still any water escaping.

For cracks or holes in the pipework, turn off and drain the system. Replace the section of damaged pipe. Tip: It's worth keeping an emergency plumbing repair kit in a kitchen drawer for this sort of problem. If one radiator doesn't heat up... If the rest of the system is working but you have a cool radiator, make sure the manual, or thermostatic valve if fitted, is open enough for water to pass into the radiator. If this doesn't work, the lockshield valve at the other end of the radiator may not be properly open. This can be adjusted with an adjustable spanner. This valve is open by a set number of turns to keep the system working efficiently. If you have to adjust it to make the radiator work, have the system checked by a heating engineer. If one part of the house doesn't warm up... This often indicates a problem with the zone valve that controls that part of the system. Time to call in an engineer. If there are knocking noises... Knocking noises are usually a symptom of a blockage or heat build-up in the system. This is usually a job for a tradesman but make sure the problem isn't simply caused by a lack of water to the boiler. Go into the loft and see if the feed and expansion tank is empty. If water flows into the tank when you move the float up and down, replace the float valve unit. If no water enters the system, it may be that the mains water supply has been cut off or a pipe has frozen. For more information see the Institute of Domestic Heating & Environmental Engineers.