Repressurise a boiler
Save £50–80 today
10 mins · Beginner · Saves £50–80 vs a heating engineer
Last updated: March 2025
Before you start
If your boiler has an error code or your radiators are cold throughout the house, check the pressure gauge on the boiler front. If it reads below 1 bar, the system needs repressurising.
This is a safe, straightforward job on any sealed central heating system (the most common type in UK homes). It takes 10 minutes.
Tools needed
- ✓No tools needed — everything required is already on your boiler
Check the pressure gauge
Look at the pressure gauge on the front of the boiler. It is usually a dial or digital display. Normal pressure is 1–1.5 bar. Below 1 bar means the system has lost pressure and needs topping up.
Where beginners go wrong
Overfilling past 2 bar — the boiler will lock out again and you will need to bleed a radiator to release pressure.
Not closing both valves before removing the hose — water will spray out.
Assuming the boiler needs repressurising every week — if pressure keeps dropping, there is a leak in the system that needs a heating engineer.
Stop and call a heating engineer if...
The pressure gauge rises immediately after repressurising and trips the relief valve — there is too much water in the system
You cannot find the filling loop or it appears damaged
The boiler pressure drops again within a few days — there is a leak that needs finding
Cost breakdown
What you just learned
You now understand how a sealed central heating system holds pressure and how to restore it. This gives you the knowledge to understand boiler error codes and when to call for help.
What this unlocks
You can now bleed radiators, identify pressure loss patterns, and have an informed conversation with a heating engineer about any persistent issues.
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⚠️ Watch out if you rent
Repressurising a boiler is normal maintenance you can do yourself. If you need to do it more than once a month, report it to your landlord in writing — a persistent pressure drop means a leak that is their responsibility to fix.