EducationalTips and Tricks

How to bleed your radiators

If you have ever put your heating on and noticed the radiators are lukewarm, then you could be experiencing air bubbles that are trapped in the system.  This is a big sign as to when you need to bleed your radiator. These bubbles prevent hot water from circulating effectively, so radiators aren't as hot as they should be and take longer to warm your home (meaning extra money and energy is being wasted). Inefficient heating can also lead to mould and damp - the uneven heat and drop in temperature in your home, causes water and moisture in the air to form on surfaces and walls.

Not only will knowing how to bleed a radiator make your heating more efficient, but ensuring that you keep your boiler in peak condition as an addition to this can save you money on your heating costs.

Before you begin the task of bleeding your radiators, you'll need to check for blockages in the system. Firstly, turn the gas central heating on and make sure that each thermostatic valve (TRV) is on full power and there is nothing in the way of it. This is important because TRVs work by sensing the surrounding air's temperature which will ultimately be affected if you have them covered up. You can usually find the TRV at the bottom/top corner of your radiator.

Once the heating has warmed up, check how hot each of the radiators are in turn. Air bubbles in the gas central heating system rise, so you'll find air collects at the top of radiators and steadily gathers, making your home colder as the problem worsens.  This means that if a radiator isn't heating up, or is cool at the top and hot at the bottom, you'll need to learn how to bleed it.

Read below for the six steps of how to bleed your radiators.

  1. The first, and one of the most important steps is to ensure that you have turned the central heating off. If you don’t, you could risk boiling water spraying out of the radiator when you bleed it, which is also another good reason to wait until the system has cooled down.

2. Grab your tools: It’s always recommended that you find a dry cloth like a tea towel and a bowl or tray to catch water. The only specialist tool you will need is a radiator key, which you can get cheaply at most DIY shops. You could use a pair of strong, narrow pliers but you could also risk damaging the valve, so it is always advised to use a radiator key if you can.

3. Find the square bleed screw at the top corner of your radiator, place the bowl or tray directly underneath it at the base of the radiator.

4. Then, place the radiator key over the bleed screw (it should fit snugly), cover it with another cloth and slowly turn the key anti-clockwise for about half a turn. You should hear a hissing sound as the air releases. At this point, hold the cloth close to prevent water dripping or spitting onto the radiator.

5. Once the air stops hissing and the water begins to trickle out steadily, tighten the screw again, being careful not to over-tighten and damage the valve. Be sure to wipe down the radiator after to avoid leaving any moisture. Leaving moisture could cause rust over time which would cause you further issues.

6. Switch the heating back on and check the boiler pressure. If it's below the optimal level, you may need to boost it by using the filling loop on your boiler. This is usually a tap or lever on the main water supply to your boiler. Finally, check that all the radiators are heating evenly and that none of the bleed valves are leaking. You may need to bleed some radiators a second time, but if the problem still isn't resolved, contact a heating engineer.

Hopefully your radiators will now all be heating effectively, leaving you with a nice warm house which you can now put your feet up with a nice brew!