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How To: Deal with Boiler Issues

Thursday, November 24, 2016

A guide to handling typical boiler problems.

As the weather turns cold, boilers become more prone to problems. In addition to complications from the cold itself, many issues arise because the systems are coming back on again after months of disuse in the summer.

As a safety precaution, it’s always best to call an expert to assist with any boiler issue. Generally, repair companies will need to know whether your boiler is gas or electric so that they can send out the right kind of engineer; be prepared with this information before calling.

Here are some of the most common boiler issues and the best ways to identify and treat them.

No heat or hot water

The most common complaint about a boiler is also the easiest to notice – it’s not heating up. While the symptom may be obvious, the cause is generally much more complicated. In fact, many of the issues listed below can lead to heat loss if untreated.

Broken diaphragms, airlocks or mechanical valves will all lead to a loss of heat, as will issues with the thermostat or low water levels. If the cause isn’t immediately obvious, it’s best to have an engineer assess it.


As with any system using water, there is always the potential for a leak to occur. These are often caused by a broken or eroded component, such as the pressure valve or a pump seal. As there are a variety of causes, it is also best to call an engineer to examine any leak.

If you have an electric boiler, turn it off at the fuse box to prevent any water from coming into contact with electrical components.

Thermostat issues

You should always check that the thermostat is working properly if you find your heating is not coming on. Look in the manual for your particular model’s troubleshooting guide. Make sure the thermostat is on and set to the correct time and temperature. If it still isn’t functioning properly and you’ve ruled out any other causes, consider having the thermostat looked at or replaced.

Banging noises and kettling

If your boiler starts making banging noises, it usually means there is air trapped in the system or the water pressure is low. If the noises sound more like a kettle boiling, then the issue may be kettling, which occurs when deposits of limescale or other minerals build up near the heat exchanger and the water starts to overheat. When the water turns to steam, it creates these distinctive sounds.

In either scenario, the best course of action is to have a plumber flush the system. If left untreated, kettling will make your boiler more expensive to run and can have other detrimental effects on the rest of the system, so it is best to deal with it quickly.

Loss of pressure

Drops in pressure can cause your heating system to malfunction. Check the pressure gauge built into your boiler as a first step to verify that the pressure is low. If there is no visible leak in the system, you can try to repressurise it yourself, but only if you feel comfortable following the steps in the manual. If not, or if there is a visible leak, it is best to contact an engineer to deal with the issue.

Pilot light extinguished

If you have a gas boiler that’s not working properly, it’s always good to check that the pilot light hasn’t gone out. This can occur when there is an issue with the gas supply or as a result of draughts and dirt build-ups. It’s always good to check the gas supply whenever the pilot light goes out and ensure your other gas appliances are still working.

While most boilers include instructions for relighting the pilot light yourself, it is generally wiser to have a Gas Safe registered engineer do so.