How to turn off a radiator, and turn it back on

Find the two valves on the radiator

Most radiators have a valve at each bottom corner. One controls the radiator day to day and the other is set once by the installer. Before you turn anything, work out which is which.

The control valve is usually the larger one with a numbered head, often 0 or * to 5 or 6. That is a TRV. Older radiators and some bathroom towel rails have a manual valve instead, a plain round or square head with no numbers, sometimes marked with open and closed arrows. The valve at the other end is normally smaller, with a plain plastic cap and no markings. That is the lockshield, which balances how much hot water the radiator gets compared with the others in the house.

Turning a radiator off for everyday use

For a room you are not using, you rarely need to shut the radiator completely. Turning the TRV to its lowest setting is enough, and it is kinder to the system.

• Turn the TRV head clockwise to 0, or to the snowflake or * symbol if it has no 0. The * setting is frost protection: the valve stays shut unless the room gets very cold, then opens a little.
• On a manual valve, turn the head clockwise until it stops. Do not use pliers on a plastic head.
• Leave the lockshield alone. It is not a daily control, and turning it changes how the whole system is balanced.
• Give it an hour and feel the radiator. It should cool from the top down. If it stays hot, the valve may not be closing (see below).

Setting a TRV to 0 does not always shut it completely. Some heads have a small amount of travel left even at 0. If you need the radiator definitely off, close the lockshield too.

Isolating a radiator completely

You need both valves shut if the radiator is leaking, if you are painting or papering behind it, or if you are going to drain it or take it off the wall. With both closed, no water can get in or out of the radiator itself.

Turn the heating off first and let the radiator cool. Then:

• Close the control valve by turning the TRV to 0 or the manual valve clockwise.
• Pull or unscrew the plastic cap off the lockshield. Underneath is a small square or hexagonal spindle.
• Turn the spindle clockwise with a lockshield key or an adjustable spanner, counting the turns (and half-turns) until it stops. Write the number down and keep it somewhere you will find it.
• Put a towel under both valves. A drip or two is normal. A steady drip means one of the valves is not sealing or the leak is coming from the valve itself.

Do not force a lockshield that will not move. Old brass spindles can snap, and then the valve cannot be shut or reopened until it is replaced. That repair needs the system drained or the pipe frozen.

Turning a radiator back on

Open the lockshield anticlockwise by exactly the number of turns you counted, then put the cap back on. Set the TRV back to its usual setting, normally around 3 for living rooms. Put the heating on and check both valves for drips while the radiator warms up.

If the radiator heats at the bottom but stays cold at the top, air got in while it was isolated. Bleed it with a radiator key. If you lost the turn count, open the lockshield about one full turn as a starting point and adjust from there: our guide to lockshield valves explains how to set it by feel or with a thermometer.

Is it OK to turn off radiators in rooms you don't use?

Turning down radiators in empty rooms is a sensible way to use less heat, but turning them fully off for weeks is not ideal. A cold room is more likely to get condensation and mould, especially on outside walls and behind furniture, and pipes in that room are more exposed in a hard frost. Setting the TRV to * or 1 and keeping the door shut is usually a better balance.

Do not turn every radiator in the house off. The room with the wall thermostat should keep its radiator on, ideally with no TRV or with the TRV fully open, otherwise the thermostat and the radiator fight each other. And the boiler needs somewhere for water to go: if every TRV is shut, it may cycle on and off or the pump may run against closed valves, depending on how the system was installed.

The NHS advises heating the rooms you use regularly to at least 18°C, particularly for older people, babies and anyone with a health condition. Our guide on when to turn the heating on covers setting up a schedule for the season.

When the radiator will not turn off

If a radiator stays hot with the TRV at 0, the usual cause is the pin inside the valve body. The TRV head presses down on a small pin, and after a summer off that pin often sticks in the open position. Take the head off (most unscrew or unclip), check whether the pin moves up and down, and if it is stuck, tap it gently or work it with pliers. Our page on a TRV stuck or not working walks through this.

If the radiator stays hot with both valves shut, one of them is passing water, and it will need replacing. The same applies if water keeps coming from a valve after it is closed, or if the spindle weeps when you turn it. A leaking radiator valve is not an emergency if you can catch the drips, but it will not fix itself, and water under floorboards can do far more damage than the valve costs to replace.

When to call us

Call if a radiator is leaking and will not stop with both valves closed, a valve spindle is stuck or has snapped, or you need a radiator taken off and refitted for decorating and would rather not drain it yourself. We have 10 vans covering London and everywhere inside the M25, 24 hours a day. Our call-out charge is £60.

Tell us which valve is leaking or stuck, whether the radiator is upstairs or down, and whether your boiler is a combi or has a hot water cylinder. That tells the engineer what to bring, including replacement valves if needed.