Before you start

Your boiler’s manual (if available)
A small container or cloth
15 minutes

For a boiler to run properly the system pressure should usually be 1–1.5 bar when cold. Below 1 bar the boiler may show a fault.

Steps vary slightly by brand. If unsure, check your manual or call an authorized technician. If you smell gas, don't touch anything and call your gas emergency line.

Step 1 of 6

Turn off the boiler and let it cool

Switch off the boiler and wait for the radiators to cool down. Pressure reads higher when the system is hot.

Step 2 of 6

Read the pressure gauge

Check the gauge (manometer) or digital display on the front panel. If it is below 1 bar, you need to top up.

Step 3 of 6

Find the filling tap

The tap is usually at the bottom of the boiler between the pipes — a small blue or black valve or a lever.

Step 4 of 6

Open the tap slowly

Turn the tap counter-clockwise slowly. You'll hear water flowing — keep your eyes on the gauge.

Around 1.5 bar is enough. Overfilling makes the safety valve discharge water.

Step 5 of 6

Close the tap firmly

Once you reach the target, close the tap firmly clockwise. Forgetting to close it lets the pressure rise too high.

Step 6 of 6

Turn the boiler on and check

Switch the boiler back on. If there's an error code, press Reset. Check the pressure again after a few hours.

Pressure between 1–1.5 bar
No error code

Congrats, you’re all done! 🎉

If the pressure keeps dropping, there may be a leak in the system. Ask an authorized technician to check it.

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