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Central Heating Repairs

Modern central heating systems are very reliable, but there are instances where repair or maintenance may be required. One of the key advantages to central heating systems is that they are energy efficient and economical.

In the UK today the price of energy is at an all time high, and many people are focussing on their energy consumption in an effort to reduce their carbon emissions and save money on heating bills.

If your heating system has developed a problem it will not be running at optimum efficiency, and is likely to be costing you more than necessary to heat your home.


As soon as you notice any difference in the amount of heat coming from radiators, the sounds coming from the boiler, or the size of your energy bill, you should take steps to have the system repaired.

In most cases it will be necessary to call in a qualified plumber or engineer, but there are some relatively easy repairs that you can carry out yourself without the cost of a professional.

Call in the repair man if you detect a difference in radiator heat,sounds from the boiler, or the size of your energy bill.

Central Heating System Being Repaired


Problems with central heating

Some of the more common types of central heating repair are detailed below, but before commencing any work, or calling in a plumber, it is important to assess the symptoms of the problem to try and diagnose the fault:

  • If the heating is diminished or you hear kettling sounds from the boiler, there is a good chance that the system has become blocked with sludge and debris, in which case it will need flushing.


  • If radiators are cold lower down and hot at the top, it may also indicate a blockage; while radiators which are warm at the bottom but cold at the top may just need bleeding of air to allow proper circulation of the hot water.


  • If the heating is working upstairs but not downstairs, there could be a problem with the pump not circulating the water correctly, and it may need to be replaced.


  • Any signs of water damage around a radiator or a piece of pipe work would indicate a leak, and the system will have to be drained, so that the leaking section can be replaced.


  • If the boiler is turning on and off as normal but the house or the domestic hot water is not warm enough, it could just be a case of a thermostat which is faulty or not set correctly; although this could also point to a problem with the boiler or the flue, which will have to be dealt with by a gas safe registered engineer.


Bleeding the radiators

If you find that the radiators are not heating higher up, it is very likely that air trapped in the system is preventing the water from circulating fully through the radiator.

Radiators have a special bleed valve designed to allow you to purge the air from the system and this is something you can do with each radiator in turn without calling in a plumber.

A bleed valve is provided on radiators to allow you to remove air from it.

Bleeding A Radiator.

The valve is located at the top and to one side of the radiator, and you should have a radiator key to turn the valves; if not you can buy a replacement fairly cheaply from a DIY shop.

Turn off the central heating so no more air can enter the system.


The radiator valve should be turned about a quarter turn anti-clockwise, at which point you will hear the air escaping. Once water begins to dribble out, it means that all the air has been removed and the valve can be retightened.

Bear in mind that the water could be very hot, and you should protect your hands with gloves or thick cloths when carrying this out. It is also worth laying a towel on the floor to protect the carpet from any drips while the radiator is bled.


Replacing radiators or pipe work

If you have a leak in the central heating, the entire system will need to be drained down to enable the replacement of the faulty part. Draining the system is explained later, and although it is not a simple task, if you are confident with DIY it is something you can undertake yourself. Make sure you have a replacement radiator or length of pipe ready for the job and simply replace like-for-like once the system is drained of water.


Replacing the pump

Most pumps are installed with an isolation valve either side, so they can be replaced easily without draining the system. Make sure the central heating is turned off and that you have a pump which is equivalent or better than the one you are replacing.

Check the speed setting on the pump you remove, and set the new one the same. Most modern boilers require pumps to be at their highest speed settings to give maximum performance, but some newer pumps are able to adjust automatically to the optimum speed for your particular system.


Draining the system

If you need to drain the system to carry out central heating repairs, you may have reached the point where you are uncomfortable working on the system yourself, and you choose to call in a qualified plumber. It is a large DIY job, and not something you should undertake if you are not completely familiar with your system.

In brief, the central heating should be turned off, and the water supply to the header tank isolated. A hose is connected to the lowest drain valve in the system, and bleed valves are opened to allow the water to escape. Once repairs have been carried out, the system is refilled and can be rebalanced to make sure it works at its most efficient.


Power flushing

The build up of rust, sludge and debris in the boiler, the radiators, and the pipe work, may require a power flush to clear it all out and restore the system to full operation. This is done after a system has been drained, by pumping a cleaning solution through the system at high velocity to remove the debris.

It may be essential if your central heating system is failing because of the sludge, but unfortunately, it is quite expensive and something you will need a professional to carry out for you.


Boiler repairs and replacement

Gas and oil boilers are complicated systems, and should only be touched by registered technicians. Particularly in the case of gas, only a gas safe registered engineer should remove the case or carry out work on the boiler. If you have any reason to suspect that the boiler is at fault, you should contact a suitable contractor immediately to repair the problem.



If your central heating develops a problem it is worth trying to diagnose the fault to give you an idea of whether you can repair it yourself or you need the assistance of a professional. You can carry out some minor repairs yourself, and it could save you the cost of calling out a plumber.

However, if you believe there is a problem with the gas or the boiler, it is best not to take any chances and to call in a fully qualified engineer at the earliest opportunity.

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