Why is my boiler losing pressure?
Most combi boilers should sit at 1 to 1.5 bar on the pressure gauge when the heating is off. If it keeps dropping below 1, the boiler may lock out and stop heating.
Common causes
- You've recently bled the radiators. Letting air out also lets pressure out, so a top-up afterwards is normal.
- A small leak. Check under radiators, around valves and below the boiler for damp patches or drips.
- A faulty pressure relief valve. Look for a small copper pipe outside, near the boiler, that drips or leaves a wet mark on the wall.
- A failed expansion vessel. The pressure shoots up when the heating is on and then drops back.
Topping up the pressure
Most boilers have a filling loop: a silver hose or a built-in key underneath. Open the valves slowly, watch the gauge rise to about 1.2 bar, then close them. Your manual will show the exact steps for your model.
When to call an engineer
If you have to top up more than once a month, something is leaking or failing. Leaving it can damage the boiler, so it's worth getting it looked at sooner rather than later.
Need it sorted? Boiler repair in Newcastle typically costs £150 to £450. A local engineer will give you a price before starting.