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How to Fit a Radiator Thermostat

Thermostatic radiator valves are a fantastic way of keeping your energy bills and carbon emissions down.

They work by detecting the temperature of the room and control the heat level of a radiator to ensure the temperature within the room is always at a constant. With thermostatic radiator valves, you would typically find numbered calibrations and a frost setting for rarely heated rooms.

To help you along the way with updating your radiator to thermostatic controls, we’ve compiled a simple step-by-step guide to how to replace your radiator thermostat:


So to start, you will need the following:

• Adjustable spanner(s)

• Plumbing taps (PTFE tape)

• Screwdriver

• Radiator bleeding key

• Large bowl or container

• Old towels or sheets

• Radiator spanner

• Junior hacksaw


Step 1: Drain the heating system

The first task involved in fitting a radiator thermostat is to drain your central heating system. It’s always better to fit any thermostatic valves in one go as the process involved in draining your central heating system can sometimes be quite intensive and time consuming. If you need to drain the water system of your home we have a handy guide which you can find by clicking here.


Step 2: Unscrew the old thermostat adaptor

Place plenty of towels or old sheets on the floor around the radiator. Using one of the adjustable wrenches, hold the body of the old valve and use the other to loosen the nuts that hold the valve onto the copper pipe. At this stage, you should not be able to remove the valve. Unscrew the adapter from the radiator and you may need to use a radiator valve that is fitted inside the adapter.


Step 3: Fit the new thermostat adaptor

Fit the new adapter, olive (metal collar) and cap nut onto the radiator. Give the internal heads a bit of a clean as they tend to pick up dirt over time and then wrap some plumbers tape (PTFE tape) around the adapter threads about 6 times in a clockwise direction. Screw the adapter into the radiator and tighten as necessary.


Step 4: Remove and replace the olive and cap nut

Start by removing the old olive and cap nut from the copper pipe and replace with the new set. Sometimes, the old olive might have become a little tricky over time and will not slide off. If this is the case, carefully cut part way through the olive with a hacksaw and break the pieces apart using a screwdriver. Under no circumstances should a hacksaw blade touch the copper pipe.


Step 5: Tightening the cap nut

Fit your new thermostatic radiator valve into place and tighten the cap nut between the adapter to the valve whilst making sure that you hold the body of the valve with one wrench. To finish the process, tighten the cap nut between the pipe and the new thermostatic valve.


Step 6: Refill your heating system

Finally, refill the central heating system within your home and check around each radiator for any leaks. At this stage it will be worth checking each of the radiator valves is functioning correctly by allowing the room to cool and using the thermostat to monitor the temperature change and increase the heat accordingly.

Please note that this guide is a rough step by step guide. Replacing some radiator thermostats will require a slightly different method so if you don’t feel confident with the valve replacement, make sure that you hire a plumbing professional to carry out the work for you.

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