Draining your central heating system

When you've found out which of the radiators in your home’s heating system need bleeding, follow these simple steps:

Top tip: If you're bleeding more than one radiator, start with the one furthest away from your boiler. If you’re living in a two or more storey house, start with the downstairs radiators before repeating upstairs.

1. Make sure your heating is off and the radiators are cold.

2. Hold an old cloth, or a jug, under the bleed valve, and insert the bleed key.

3. Turn anti-clockwise until air starts escaping (you'll hear a hissing noise).

4. When water starts to escape, turn the key clockwise to re-tighten the valve.

5. Repeat on other radiators that need attention, making your way back towards the boiler.

6. Turn your heating back on and check if your radiators are now heating up correctly.

Bleeding your radiators is how you get rid of the air pockets that stop hot water circulating around your central heating system efficiently. This puts more strain on your boiler and costs you more money.

It’s important to note that bleeding your radiators is not the same as draining or flushing your central heating system.

If bleeding your radiators doesn’t fix your heating problems, your radiators may need to be drained and flushed. Flushing refers to cleaning out magnetite from your heating system that has developed over time. This is the term used for the dissolved metal that appears as a black sludge in your radiators. We recommend getting a professional to flush your system.

Luckily, bleeding your radiators is easy to do and only takes a few seconds, so your home will soon be warm again.

There are a few ways to tell if your radiators need bleeding. For instance, they may be taking longer than usual to heat up, or you may be hearing gurgling noises.

A good way to check if your heating system needs bleeding is to see if your radiators have cold patches at the top but are warm at the bottom. If so, you need to bleed them to let the trapped air escape and the hot water to circulate freely once again.

You don't need any complicated equipment to bleed a radiator. All you need is two things:

• A radiator bleed key, which can be bought from any hardware shop for under £2 – or a flathead screwdriver.
  
  
• An old cloth or a jug to catch any escaping water.

A bleeder valve is where you put the radiator bleed key. The bleeder valve on the radiator is usually situated at the top of the radiator and can be at either end.

It's round and has a square section in the middle with two notches. This is where you put the bleed key (or screwdriver) to drain the radiator to let the trapped air escape.