Bleed a radiator
Save £50–80 today
15 mins · Beginner · Saves £50-80 vs a heating engineer
Last updated: January 2025
Before you start
Do this if your radiator is cold at the top but warm at the bottom — that means trapped air is preventing hot water from circulating.
You need a radiator bleed key (about £1 from any hardware shop) and a cloth or small container to catch drips.
Tools needed
- !Radiator bleed key — buy: £1–3 from any hardware shop
- ✓Old cloth or small container — to catch drips, any household rag will do
Turn off the heating
Switch off your central heating and wait 20–30 minutes for the radiators to cool. Never bleed a hot radiator.
Where beginners go wrong
Opening the valve too far and letting too much water out, dropping the boiler pressure.
Not placing a cloth under the valve and getting water on the floor.
Forgetting to check boiler pressure afterwards, causing the boiler to cut out.
Stop and call a heating engineer if...
The boiler pressure keeps dropping after you top it up
The water coming out is black or very murky
The radiator is still cold all over after bleeding
Cost breakdown
What you just learned
You now understand how central heating systems circulate water and why air gets trapped. These skills transfer to balancing radiators and maintaining your boiler pressure.
✅ Completed by 6,104 people
How long will this actually take me?
First time
15–20 mins
With experience
5 mins
The hardest part is usually finding the bleed key — have it ready before you start.