How to top up your boiler pressure & reset your boiler

Keeping your boiler running smoothly often comes down to two simple tasks: topping up the pressure and resetting the boiler when needed. Here’s a straightforward guide to help you do both safely.

Why boiler pressure matters

Your boiler needs the right amount of water pressure to circulate hot water around your home. Most boilers work best between 1.0 and 1.5 bar when cold. If the pressure drops too low, your heating may stop working or the boiler may lock out.

How to top up (repressurise) your boiler

1. Check the pressure gauge

Look at the front of your boiler — you’ll see a dial or digital reading. If it’s below 1 bar, it’s time to top up.

2. Find the filling loop

This is usually a silver braided hose underneath the boiler with two small valves.

3. Open the valves slowly

Turn both valves so they line up with the pipe. You’ll hear water flowing into the system.

4. Watch the gauge rise

Once it reaches 1.2–1.5 bar, close both valves firmly.

5. Turn the heating on

Your boiler should now run normally. If the pressure drops again quickly, you may have a leak — time to call an engineer.

How to reset your boiler

Most modern boilers have a simple reset button. Here’s how to use it safely:

1. Check the display for an error code

If your boiler has locked out, it will usually show a fault code.

2. Press and hold the reset button

Hold it for 3–5 seconds (varies by model). The boiler should attempt to restart.

3. Wait for the boiler to fire up

It may take a minute or two to run through its safety checks.

4. If It keeps locking out

Don’t keep resetting it — this can cause damage. A persistent lockout usually means a deeper issue that needs a qualified engineer.

When to call a professional

• Pressure drops repeatedly

• You see visible leaks

• The boiler won’t reset

• You smell gas or suspect a safety issue

A quick visit from a Gas Safe engineer can prevent bigger problems later.