What Pressure Should My Boiler Be?
Not sure if your pressure is too high or low? Don't worry. It is a simple fix, and knowing what to look for can save you time and stress.
What is the Right Pressure?
Most modern combi and system boilers are happiest when the pressure gauge reads:
❄️ When Cold
Between 1.0 and 1.5 bar. This is the ideal resting pressure for your system.
🔥 When Heating is On
Up to 2.0 bar. It is normal for pressure to rise slightly as the water heats up and expands.
Where is the gauge? You will usually see it on the front of the boiler or just underneath. It often has a green 'safe zone' to help you spot if it is in the right range.
What If Pressure Is Too Low?
If the needle drops below 1.0 bar (and especially under 0.5), your boiler might shut itself down as a safety precaution.
⚠️ Signs of Low Pressure
- No heating or hot water
- Boiler won't ignite
- Error codes (e.g. E118 on Baxi, F75 on Vaillant)
🛠️ How to Fix It
You can usually fix this by topping up the system using the filling loop (a silver braided hose or key).
Open the valves slowly until the gauge hits 1.2 bar, then close them tight.
If you are not confident doing this, give us a call. We are happy to walk you through it.
What If Pressure Is Too High?
On the flip side, if the pressure creeps above 2.5 bar or hits 3.0, your boiler is under strain. You might see water dripping from the overflow pipe outside.
Common Causes:
- Overfilling: You added too much water when topping up.
- Expansion Vessel: The internal component has failed or lost charge.
- Filling Loop: The valves aren't fully closed, letting mains water in.
Need a Hand With Boiler Pressure?
We help homeowners across Fife & The Lothians with pressure problems every week.
Whether it is a simple top-up you are unsure about, or a faulty part that needs replacing, we will get it sorted quickly.
Call 01383 660098Book Boiler Repair Online