Why Does My Boiler Keep Losing Pressure?
If your boiler pressure keeps dropping below 1 bar, it is usually caused by a leak in the system, a faulty pressure relief valve, or bleeding radiators.
What is normal boiler pressure?
Most combi and system boilers should sit between 1 and 1.5 bar when the heating is off. When the heating is running, it can rise to about 2 bar. If your pressure gauge regularly drops below 1 bar, something is causing water to leave the system.
Common causes of pressure loss
The most common reason is a small leak somewhere in the system - this could be at a radiator valve, a pipe joint, or the boiler itself. A faulty pressure relief valve can also let water escape through the overflow pipe outside. If you have recently bled your radiators, that releases water from the system and will drop the pressure too.
How to repressurise your boiler
Find the filling loop - it is usually a small braided hose underneath the boiler with one or two taps. Open the taps slowly and watch the pressure gauge. When it reaches about 1.2 bar, close the taps. If you are not sure where the filling loop is, check your boiler manual or give us a call.
When to call an engineer
If you are topping up the pressure more than once a month, there is an underlying problem that needs fixing. Repeatedly topping up masks the issue and can lead to further damage. We will find the leak or faulty component and sort it properly.
Can low pressure damage the boiler?
Most modern boilers will lock out and display an error code if the pressure drops too low, which prevents damage. But running at low pressure means the system is not working efficiently, and ignoring a leak will only make it worse over time.
Need help with this?
Call us on 01932 943 009 or email info@hphsolutions.co.uk. We cover Surrey, Hampshire, Berkshire and London. Free quotes, no obligation.
