Whilst this can be worrying, there is a very high chance that it could simply be due to how most sealed central heating systems work these days. Just stay calm and patient, don’t overdo it and be ready to stop before you do any damage then call in the experts!
What counts as “too high”?
The boiler pressure gauge as standard is located on the front of most UK combination and sealed systems but if unsure, locate the manufacturer’s manual. The heating being on will bring it up a little bit. Usually when it is going over 2.5 – 3.0 bar or even in the red that would be too high. Ideally a friction reduction additive mixed with oil should be applied.
First step: Turn the heating off and allow it to cool
With the system heated, high pressure can often appear even worse. Turn off your heating and leave for 30 to 60 minutes. If the pressure returns to normal when it is cool, you might have a high spike but it’s an isolated incident.
Step 2: Check the filling loop
Has the filling loop been left open after topping up? (Very common reason for high pressure)
The filling loop (usually a silver braided hose under the boiler)
Verify that both valves are completely closed.
Pro Tip : when in doubt, do not try to make stiff valves comply – call an engineer instead. For Boiler repair Cheltenham, contact combi-man.com/
Step 3: Bleed a radiator
If the system is cold and pressure still applies, bleeding a radiator can relieve some water to lower the pressure.
Place a cloth/container under the valve
Slowly let out air then firmly close.
Re-test the pressure after every radiator. Don’t overdo it.
When should you turn the boiler off:
Turn off the boiler and call a Gas Safe engineer immediately if:
The pressure is about 3 bar or at the top of the red
Dripping or running outside PRV = pressure relief valve
Leaking, banging or boiler fault code displayed.
Why it occurs
If pressure continues to rise, it could suggest problems such as a defective expansion vessel or issues with the filling loop. These aren’t DIY fixes.
Book a boiler review now before the boiler has the chance to break down.