Radiator Valves, TRVs and Heating Zones: A UK Homeowner's Guide

If one room is too hot while another stays cold, the cause is often the valves on your radiators or how the heating circuits are set up. This guide explains thermostatic radiator valves (TRVs), lockshield valves and zoning in plain English, based on advice from the Energy Saving Trust and a valve manufacturer.

What a TRV does

A thermostatic radiator valve controls how much hot water enters a radiator, based on the temperature of the room. According to the manufacturer Altecnic, inside the valve is a temperature-sensitive element filled with liquid or wax. It expands or contracts with the room temperature. As the room warms, the valve closes slightly; as it cools, more hot water flows in. Depending on the model, it can be fitted on the flow or the return side.

The Energy Saving Trust says TRVs help you control the temperature of individual rooms.

Using TRVs well

Set each TRV to the lowest setting that keeps the room comfortable, as the Energy Saving Trust advises.
Numbers on the dial differ between models, but lower numbers generally mean a cooler room.
Avoid radiator covers: the Trust says they can stop the valve reading the room temperature accurately.
Altecnic adds that the sensor head should be kept away from heat sources and not blocked by curtains or furniture.
Altecnic also says TRVs should not be fitted in the room that has the central thermostat, because conflicting readings can result.

Lockshield valves and balancing

The other valve on a radiator, usually at the opposite end, is the lockshield. Altecnic states that you adjust lockshield valves to control flow rates. Its outline of balancing is:

Fully open the TRVs.
Run the heating to normal temperature.
Adjust the lockshield valves.
Check that every radiator heats evenly.

Balancing can take patience, and it affects the whole system. If you are unsure, ask a qualified heating engineer. We have not verified details such as temperature drops between flow and return, so we give none here.

Zoning: heating parts of the house separately

The Energy Saving Trust explains that zone controls use separate programmable heating circuits for different parts of the house, usually upstairs and downstairs. They let you heat different areas at different times automatically. The Trust suggests zone controls for new heating systems and says they may be needed to meet building regulations in large homes. For existing systems it says programmable TRVs may be a more practical solution.

What about zone valves?

A zone valve is the motorised valve that opens and closes a heating circuit in a zoned system. Neither of the two sources we checked explains zone valves in detail, so we do not describe wiring, faults or settings here. Not verified: beyond that general role. Ask a qualified heating engineer about your own system.

Possible savings

The Energy Saving Trust gives these estimates:

Installing and using heating controls effectively could save around 100 pounds a year in Great Britain and 110 pounds in Northern Ireland.
Turning the room thermostat down by one degree, from 22C to 21C, could save 120 pounds in Great Britain and 80 pounds in Northern Ireland.

These are estimates for typical homes, published by the Trust. We do not know the date of the figures, and your own results will depend on the house, the fuel price and how you use the heating.

Common problems to ask about

A radiator that stays cold at the top or bottom, or a TRV that seems stuck. Do not force parts; ask an engineer.
Rooms that heat unevenly even with TRVs fully open. The balancing steps above may help, or an engineer can assess it.
A cold room that has a TRV near a draught or heat source. Check where the sensor head sits.

Who should do the work?

Draining a system, replacing a valve or working on circuits should be done by a competent, qualified heating engineer. We have not verified specific registration or certification rules for your situation, so please ask any installer to show their credentials and check what applies.

Comparing quotes

Ask for the valve type and brand, whether the price includes draining and refilling the system, balancing, warranty and timing. Compare total cost, not only the cost of the valve.

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Request a quote

Tell us what you need (TRV replacement, balancing, zoning) and your postcode area, and we will forward your request to heating engineers and suppliers near you.

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General information only. Not engineering, legal or financial advice. Have a qualified heating engineer assess your system.