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Common Problems with TRVs and Maintaining Thermostatic Radiator Valves

Oct 10,2020

There are several things that can cause problems with TRV’s, but as they are relatively simple devices it is not too difficult to diagnose the problem. It is recommended to maintain them to ensure that they last and perform well.

The most common problem with a TRV is that the valve sticks or catches. This means that they are either stuck open or closed. This will happen when the setting has not been moved for some time, such as after the summer.

Solution and Maintenance: Set the TRV to the highest heat setting (generally number 5) which will open the valve fully. Then undo the thermostat removal nut, which you should be able to do by hand. When the thermostat unit comes off, you should see the little plunger or piston, which should be able to be depressed and then should spring back up when released. If this is very stiff or catching, give it a little squirt of WD40 and work it a little until it slides freely. An annual check and squirt of WD40 is advisable to keep the TRV working efficiently.

If you cannot get the plunger working again, then the valve has failed and will need to be replaced completely. See below section on how to change a TRV for help with this.

The second problem that can occur is that the thermostat can fail. If the valve is working, and the plunger is moving freely, it is likely that the thermostat is not depressing and releasing the plunger, therefore opening and closing valve as it should. The thermostats is relatively simple which uses a trapped bubble of gas, liquid or wax to expand and contract with the change in temperature of the room to move the plunger.

Solution and Maintenance: If the thermostat has stopped working there is nothing you can do except replace it. Before you do buy a new one it is worth making sure that this is the problem, but swapping the thermostat with a working TRV and confirming that the valve now works.

For general maintenance of your TRV it is worth opening and closing the TRV fully several times to get the mechanism working. Do this several times per year to stop the plunger or piston seizing up.