6 Step Guide: How to Bleed Radiators

Why Should You Bleed Radiators?

Is your heating taking too long to get going? Are your radiators always cold at the top? It sounds like your home could benefit from a good bleed, a radiator bleed of course! How do you bleed radiators though?

A common problem for radiators is that over time air gets trapped at the top, this creates cold spots and reduces the efficiency of your home’s heating system. This has a knock-on impact on your heating bills since you need to use more energy to attain the required temperature.

So, to lower costs and improve energy efficiency in your home, it’s a good idea to know how to bleed radiators yourself. This is our super-simple 6 step guide.

How to: Bleed Radiators

  1. Preparation

You will need:

  • Towel or cloth.
  • Small bucket.
  • Radiator bleed key or flat-headed screwdriver (depending on the age and model of your radiators).
  • And, if this is your first time, it is also useful to have your boiler user instructions to hand.
  1. Identify the Problem Radiators

Start your central heating and check that every radiator is turned on. Allow time for each radiator to heat and ensure there is enough pressure in the system (this is necessary to push the air out).

Carefully check each radiator (and heated towel rail) by feeling for inconsistencies in the temperature at the top and the bottom. Any that have cool spots will need to be bled.

Other tell-tale signs are clicking, ticking or gurgling noises coming from your pipes and radiators.

Now it’s time to turn the heating off to deal with the problem.

  1. Check the Pressure

After letting the radiators cool down, find the pressure gauge on your boiler and note the working pressure when the system is cold. Why? When you bleed radiators, it releases pressure from the central heating system which may need replacing to resume pressure afterwards.

The operating water pressure for a central heating system is usually between 1.0-2.0 bar. However, this is an estimate, so don’t worry if yours falls outside this range.

  1. Bleed Radiators that are Affected

Attach the key or apply the screwdriver to the radiator valve and turn anti-clockwise. The valve will be located on the side of the radiator, or at the top of a towel warmer. Hold the cloth below the valve (in the case of any drips). Once open you will hear a hissing sound, this is the air escaping.

bleed radiators DIY

Once air has been released water will start to come out (it could be quite a jet so have a bucket ready), at this point, you need to close the valve tightly. You should gauge when the air is nearly released as the sound will change – you will hear water bubbling up through the radiator.

Repeat this process for all the affected radiators in your home.

Note: If there’s a lot of air in a particular radiator you may need to top up the pressure in the system to complete the bleed. Remember to shut the valve. Otherwise, water will be squirting out of the radiator while you are tending to the boiler.

  1. Check the Pressure Again

If the pressure on the gauge has dipped below the level that you noted earlier, you should top-up your boiler by using the filling loop (a tap or lever) on the boiler itself or the pipework nearby.

  1. Run a ‘Hot Test’ on the System

Now that your radiator bleed is complete, it’s time to check the system! Do this by turning on your heating system and waiting for the radiators to heat – check again for cold spots. If you find cold spots, repeat the process until your radiators are completely warm.

Then, simply sit back in your warmer home, content in the knowledge that it’s running at optimum efficiency!

Automatic Radiator Valves

There are other ways to solve inefficient systems if you want to avoid having to bleed radiators. That’s done by fitting automatic radiator valves. These automatic bleeders can be attached to each radiator and let air out gradually; this will depend on the type of radiators in your home, so do check before buying.

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Also, learn how to remove a radiator here.