Should all radiators have thermostatic valves?

Question

We've got a mix of TRVs and plain valves across the house. A plumber mentioned all radiators should have TRVs except the one in the room with the room thermostat. Is that right?

Guy · Accepted Answer

The plumber you spoke to is mostly right, but there is a slight nuance depending on how modern your heating system is.

Here is how your radiator valves should actually be set up for safety, comfort, and efficiency:

1. The Thermostat Room (Strictly No TRV)
The radiator in the same room as your main wall thermostat should never have a thermostatic valve fitted; it needs a standard manual valve left fully open.

Think of the wall thermostat as the master switch. If you put a TRV on the radiator in that same room, they will "fight" each other. If the TRV shuts down the radiator before the room hits the wall thermostat's target temperature, the wall stat will keep telling the boiler to run indefinitely. This wastes a massive amount of energy and overheats the rest of the house.

2. The "Bypass" Setup (It Depends on Your Boiler)
A central heating pump needs a way to circulate water if all the TRVs across the house suddenly close at once. Without an open loop, the pump will strain and eventually fail. How your system handles this determines your valve setup:

- Older Systems: Usually rely on a Bypass Radiator (typically the bathroom towel rail or hallway). If your system is older and lacks modern bypass valves, this specific radiator must have plain valves left wide open to give the water a safe route home.

- Modern Systems: Usually have an Automatic Bypass Valve (ABV) fitted near the boiler or built into the unit itself. If you have one of these, you do not need to leave a bathroom radiator open. You can put a TRV on it to prevent the bathroom from turning into a sauna.

3. All Other Rooms (Yes to TRVs)
Every other room (bedrooms, kitchen, dining room, and hallways), should have a TRV. This allows you to close off or lower the heat in unused rooms, balancing the temperature across the property and cutting your heating bills.

Summary Checklist:
To clean up your mix-and-match setup:

- Keep plain valves on the radiator in the room with the wall thermostat.

- Check with a heating engineer to see if your system has an automatic bypass valve. If it does, put TRVs everywhere else. If it doesn't, leave the bathroom towel rail on plain, open valves.

James · Answer

It’s personal preference but certainly helps with heat wastage in rooms that aren’t being occupied. He’s correct about the room with the room thermostat not needing one and they shouldn’t be installed in bathrooms either.

Jay · Answer

No, 1 rad should be without trv to work as bypass. Bathroom rad or room with room stat fitted in same room (if room stat fitted.

Neal · Answer

Hi.
Not all radiators require thermostat valves.
But this allows you to regulate each room efficiently.

Should all radiators have thermostatic valves?

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