How to Fit a New Radiator Valve
Before fitting a TRV, start the system from cold and find out which pipe on the radiator gets hot first. The new valve must go on this side, irrespective of whether the current valve is a hand-wheel or lockshield.
It’s a good idea to try the new valve in position so that you can check the fit. Make sure the flow direction stamped on the body matches the direction of flow through the radiator, and that the valve will fit in this position. Check, too, that you won’t have to alter the pipe length to suit (see Problem Solver below).
Draining the water
Before removing any valve, you should also decide how you’re going to empty the radiator. The most reliable way, particularly if you’re fitting several new valves, is to shut off the system and drain it down completely. However, there are alternatives:
♦ If you have a pipe freezing kit, isolate the far side of the radiator by closing its valve, then freeze the pipe below the valve you want to remove. This still leaves the radiator full of water, which you must catch in a bowl as you unscrew the valve connections. It can be a messy job.
♦ A Remrad kit allows you to force the water in the radiator back into the system pipes by attaching a bicycle pump to the air bleed valve at the top of the radiator.
♦ Open the air bleed valve at the top of the radiator using a radiator key. (If you’re draining as you remove the valve, open it gradually to start with.)
♦ Place a bowl under the valve to catch any drips, then unscrew the valve/pipe connection with a wrench.
♦ Unscrew the old valve from the threaded tail in the radiator.
♦ Remove the threaded tail. The best tool for this is a hexagonal Allen key. Otherwise, try turning it with an adjustable wrench using a cloth to stop the jaws slipping. If it won’t budge, warm the tail gently with a hot air stripper to soften the old jointing compound.
♦ Remove the old olive on the flow pipe. Normally this can be done by tapping the nut upwards with a spanner. If not, saw through the olive carefully with ablade.
Fitting the new valve
♦ Remove the tail supplied with the new valve. Wrap four or five turns of PTFE tape around the thread, thenthe tail into the radiator.
♦ Offer up the new valve (for a TRV, remove the sensor first), locate it against the tail, and check that the flow pipe meets the internal stop in the valve body. Then remove it and thread on the new nut and olive.
♦ Refit the valve, tighten the pipe connection as for any compression fitting, thenthe valve coupling nut to the tail.
♦ For a TRV, fit the sensor. Remote sensors screw to the wall and attach to the valve via a capillary tube.
RECOMMENDED TEMPERATURE SETTINGS
Living room 21°C
Pipe too long/too short
To avoid leaks, it’s essential that the flow pipe meets the internal stop inside the valve body; don’t be tempted to ‘make do’ if it’s just too short.
♦ If the pipe is too long for the new valve, support it in an adjustable wrench (with cloth in the jaws) while you trim it to the right length with a hacksaw.
♦ If it is too short, cut it back even further, then join in a new section. A soldered joint looks neatest here, but make sure the pipe is empty of water first, or the joint won’t ‘take’.