Valcore Plumbing & Heating in Colchester
Valcore Plumbing & Heating in Colchester

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Is your boiler losing pressure? What to do if you have low boiler pressure

What is boiler pressure?

Modern boilers are often installed as part of a sealed heating system. Unlike open systems that need a feed and expansion header tank in the loft to regulate the water in the system, sealed systems contain a fixed amount of water and can be topped up manually by opening the valve. The amount of water circulating in the pipework is measured in pressure (bars).

Correct water pressure is essential for the efficient functioning of your boiler and heating system. If the boiler pressure drops too low then your boiler may no longer function.

What causes low boiler pressure?

Commonly leaks may occur on the many joints along the pipework or inside the boiler. Leaks may even be so tiny that it can be difficult to detect, especially if the water is warm and evaporates as soon as it leaks. However, whether the leak is small or large, you will find your central heating system losing pressure.

Whilst the common cause of low boiler pressure is a leak within the heating system, a water pressure gauge which is inconsistent (alternating between high pressure and low pressure depending whether the boiler is hot or cold) may suggest that the pressure vessel needs replacing. If you see this happening with your boiler you should always call a trained Gas Safe registered engineer to diagnose and fix the fault.

How do I know if I have low boiler pressure?

The water pressure gauge or indicator is typically located on the front of your boiler. For most boilers, this should be set around 1 bar. Try to check the gauge regularly so that you can recognise any changes to the pressure.

What do I do if my boiler is losing pressure?

If you observe low boiler pressure it may be possible for you to re-pressurise the system yourself using the specific instructions in your user manual. Typically you should re-pressurise the system to between 1 and 2 bar. If in doubt, call an engineer and ask them to re-pressurise your boiler for you.

Never run your boiler if the pressure is above 2.9 bar or if your boiler has no pressure.  This can damage the parts in your boiler and may lead to these needing to be replaced.


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