How to bleed a radiator

Aug 01, 2023

Bleeding radiators can keep your bills down

If your radiators aren't heating up properly then they might need bleeding.

Bleeding a radiator can ensure that it is operating as efficiently as possible, saving you money and keeping your home warm. Radiators need to bleed if they have air stuck inside them.

The trapped air can inhibit warm water moving around the radiator, leaving them warm at the bottom and cold at the top. This reduces the radiator's ability to heat the room.

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Another reason to bleed a radiator is if it makes noise. Some can make banging, gurgling or clanking noises, but bleeding can solve this.

Fortunately, bleeding a radiator is a simple process.

Before you start, you will need a radiator key (found easily in DIY or homeware stores) and something to catch any water which may be released during the bleeding process.

You must also turn off your heating before you start. You can't bleed a radiator if it is on - it will be too hot to touch and may spray hot water out during the process.

To bleed the radiator, use the key to turn the valve at the top of it. The key will lock into the square groove in the valve.

Turn the valve anticlockwise slowly and carefully. This should produce a hissing noise, which is the trapped air escaping.

Have a cloth or a mug to catch any water that escapes. Once the hissing stops and only liquid is escaping, tighten the valve by turning it clockwise.

This should be done quickly to avoid too much water coming out.

Once you have finished each radiator that needs bleeding, you should turn the heating back on to ensure it has worked.

Bleeding your radiators can cause the pressure to drop, so you should check it by looking at the gauge on your boiler. If the pressure has dropped too low, this will need to be topped up by using the lever or tap on your boiler, known as the filling loop.

Then you should see if the radiator is heating up properly. The problem will be fixed if heat is spread evenly across the radiator.

You should make sure your heating is off and your radiators are cold when bleeding them.

No, you shouldn't. The aim is to release the trapped air and lose as little water as possible.

You should bleed your radiators once a year, even if they are working properly.

The accepted wisdom is that in a normal home with multiple floors, the first to be bled should be the radiator on the lowest floor and furthest away from the boiler. Then, you should work closer toward the boiler before moving up to any higher floors.

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