What Pressure Should My Boiler Be?
If you're unsure what pressure your boiler should be showing, you're not alone. Boiler pressure is one of the most common causes of heating system issues — but thankfully, it's also one of the easiest things to monitor and manage.
What’s the Correct Boiler Pressure?
For most modern combi and system boilers, the correct pressure is:
- When cold: 1.0 to 1.5 bar
- When heating is on: Up to 2.0 bar
It’s normal for the pressure to rise slightly when your boiler is in use and fall when it’s off or cooling down.
Where Do I Check My Boiler Pressure?
Look at the pressure gauge — usually found on the front of the boiler or just underneath. It may be analogue (with a dial) or digital, depending on the make and model. There’s often a green zone to show the safe range.
What If the Pressure Is Too Low?
If the gauge is reading below 1.0 bar (and especially below 0.5), your boiler may stop working to protect itself.
Common signs of low pressure:
- No hot water or heating
- Boiler showing an error code (e.g. E118 or F75)
Fix: Use the filling loop to top up the pressure slowly to 1.2–1.5 bar. Then restart the boiler if needed.
What If the Pressure Is Too High?
If your pressure is over 2.5–3.0 bar, your boiler may release water through the pressure relief valve or shut down.
Causes of high pressure:
- Overfilling via the filling loop
- Faulty pressure relief valve
- Expansion vessel failure
Fix: Bleed a radiator to release pressure or call an engineer to check for internal faults.
How Often Should I Check Boiler Pressure?
You should check your boiler pressure:
- Once a month as part of general maintenance
- After bleeding radiators
- If your heating isn’t working as expected
Is It Safe to Adjust Boiler Pressure Yourself?
Yes, but only within reason. You can safely top up a sealed system using the filling loop — but if pressure problems persist, or if you’re losing pressure regularly, call a professional. Too much DIY fiddling can mask deeper faults or void warranties.
Need Help With Boiler Pressure Issues?
Jones Heating helps homeowners across Dunfermline & Fife with pressure-related boiler problems — whether it’s dropping pressure, leaks, or persistent overpressure faults.
📞 Call us: 01383 660098
🌐 Visit: jones-heating.co.uk/boiler-repairs
We’ll diagnose the cause, explain your options, and fix it fast — without the jargon or guesswork.
