Property Maintenance Tips & Tricks

This series of articles is designed to help you solve some of those niggling household problems. These tips aren't intended to make you an expert, and are not a replacement for seeking professional advice where needed. Please feel free to contact us if you have any questions or comments.

How to bleed a radiator »
How to balance a heating system »
How to remove an airlock from a radiator »
Spring Maintenance Jobs »
uPVC Window/Door Maintenance & Cleaning »

How to Remove on Airlock in your Radiator

If you have bled your radiators, checked your TRV's*, and balanced your heating system, but still have one or more radiators that are cold when all the others are hot, this may indicate that you have an airlock in your system. The good news is that most of the time you can fix this problem yourself, without the need to call out a plumber. Please be careful if the heating system has been on and other radiators are hot. Just follow the steps below...

Turn off the valves at each end of the radiator.
Open the bleed valve (by turning anti-clockwise using a radiator key or screwdriver) to remove any pressure from the radiator (have a cloth or small container handy to catch any drips).
Remove the bleed nipple**, then attach your your 1/2" tail and hose*** to the bleed valve using a little PTFE to ensure a tight seal.
Make sure your heating is turned off, and if you have a pressurised system, check that you have sufficient pressure in your system (normally between 1 and 1.5 bar). If you have a tank fed system in the loft, make sure that the ball-valve is free moving and will rise or drop easily when needed.
Now you need to purge the air from the flow and return sides of the radiator:
a) Flow side - open up the TRV* valve and let the water flow into a container until it is smooth running, then close it again. If your heating has been on recently you will notice that this water is hot/warm.
b) Return side - open the lockshield valve until the water runs smoothly, then close again.
Now that you have water flowing though the system smoothly, shut both valves then remove the hose and replace the air-bleed valve securely.
Make sure that your system is topped up again if needed. For pressurised systems you may need to use the filling loop (please refer to your boiler manual).
Reset your TRV and lockshield valves as required. Turn on your heating system and test again.

After you have solved this issue, it is a good idea to try and discover the cause of the problem. This can be anything from not having enough inhibitor in your system, incorrect automatic air vent or expansion pipe positioning, or your pump speed is set incorrectly causing the water to cavitate. These jobs are best carried out by a qualified plumber.

Another cause of just one radiator being cold while the others work as expected could be a faulty TRV*. We wil deal with replacing a faulty TRV in our next article. Watch this space!

* Thermostatic Radiator Valve
** If your radiator has a built in thread for the bleed nipple, this method will not work for you
*** Use a garden hose coupled to a 1/2" male thread hose Tail adaptor

If you still have a problem with one radiator not getting hot, there can be other reasons such as sludge or debris in the radiator. This is best dealt with by a qualified plumber.

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Turning off a lockshield valve...

Turning off the TRV.

Attach a hose to your bleed valve.