How to fit a radiator: replacement and installation steps

Installing a radiator in place of an old one is one of the more manageable heating jobs. If the new radiator fits the same pipes, you don't need new pipework or to drain the whole system. You shut the old radiator off, drain it, hang the new one and refill it.

This guide shows you how to fit a radiator safely, step by step. It covers the order that keeps water off your floor, how to check your heating's pressure afterwards, and when to call a heating engineer instead.

Quick answer: Turn the heating off and let it cool. Close both radiator valves, counting the turns on the lockshield (the valve with a plain cap). Undo the nut between one valve and the radiator, and drain the water into a tray. Then undo the other side and lift the radiator off. Fit the new brackets, move the valve tails across, hang the new radiator and do both nuts up. Fill it slowly through one valve with the bleed screw open, and close the bleed screw once water runs out with no air. Then open both valves and check your boiler pressure.

When to call a professional: Call a heating engineer or plumber if the new radiator won't line up with your pipes. Do the same if you want to move or add a radiator. Call one if a valve won't shut off or leaks. If the valves themselves need changing, or the whole system needs draining, we recommend one unless you're experienced in draining, refilling and repressurising your type of system. Get help too if your boiler pressure won't hold after you've topped it up. If you have a heat pump, ask your installer before you change a radiator. Gas work, such as installing, servicing or repairing a gas boiler or gas pipes, is a job for a Gas Safe registered engineer.

Can you fit or replace a radiator yourself?

Yes. You can install a new radiator in your house yourself, without being registered. In Great Britain, the HSE says a person who isn't registered may do this "wet work". But only a Gas Safe registered engineer may work on the gas boiler itself, or make the final connection of the water pipes to it.

Being allowed to do it doesn't make it right for everyone. To replace a radiator like for like as a DIY job, you need to be happy with two spanners, a drill and a spirit level. You'll need a helper for the lifting, and care at the end, when you refill. If you're not confident, we recommend a heating engineer, as our other radiator guides do.

Read your new radiator's instructions before you start. Some makers want a qualified installer. Eastbrook says its radiators "must be installed by a fully qualified engineer", and its warranty depends on it. Stelrad says a qualified engineer or a competent person should fit its panel radiators.

Radiator replacement: what "like for like" means

This guide covers central heating radiator installation and replacement on the same pipes: a new radiator, in the same place, on your existing valves. It's a like-for-like swap when:

• The pipe centres match. The distance between the new radiator's connections, with its valves, matches the distance between your pipes.
• The connections are in the same places. Most panel radiators connect at the bottom of each end. Many towel rails and some vertical radiators connect underneath instead, which needs different pipework. Our bathroom heating guide covers towel rails.
• Your valves are in good order. The valves stay on the pipes. You only move the tails across: the short threaded pieces that join each valve to the radiator. Replacing a valve body means draining and refilling the heating. We recommend a heating engineer or plumber unless you're experienced in draining, refilling and repressurising your type of system. Our radiator valves guide explains the types, and you can browse radiator valves to choose a pair.
• The wall can take the weight of the new radiator, full of water.

If any of these doesn't apply, ask a heating engineer for advice before you buy. The job may mean moving pipes, changing valves or strengthening the wall. Stelrad says that if the pipe centres are changing, "it's best to get a plumber to do this bit".

Sealed or open-vented? Know your heating first

The water in your heating is kept separate from the water in your taps. So turning off the stop tap doesn't drain your heating or take the pressure off it. To shut off one radiator, you close the two valves on that radiator.

How you refill at the end depends on your system:

	Sealed system	Open-vented system
Boiler	Usually a combi or system boiler	A regular boiler
How to spot it	A pressure gauge on or under the boiler	A small feed and expansion tank, usually in the loft
How it's topped up	With mains water, through a filling loop (often a short hose with a valve at each end) that you open only when needed	The tank tops up the heating water by itself
After a radiator swap	Check the pressure, and top it up if it's low	Nothing to top up

On a sealed system, the heating runs under pressure. Filling a new radiator takes water from the rest of the system, so you may need to top the pressure up afterwards.

Our guide to checking and maintaining radiators explains both systems and how to top up the pressure.

Before you buy: measure the old radiator and its pipes

Measure before you order a replacement radiator, so it fits your pipes. Stelrad says matching the pipe centres "avoids costly pipework changes". Take these four measurements:

1. Pipe centres: from the centre of one pipe to the centre of the other, where they come out of the floor or wall.
2. Wall to pipe centre: from the wall to the centre of the pipes.
3. Floor to valve nut: from the floor to the centre of the nut where each valve meets the radiator. The new radiator's connections need to sit at the same height.
4. The old radiator's overall height and width, and the space you have around it.

Then check them against the new radiator's dimension drawing. Product pages list the pipe centres, but check how each maker measures them. Park Lane, for example, gives one column radiator's pipe centres as 1010mm "+ ≈90mm for valves". If your old radiator is more than about 15 years old, Stelrad says to check the replacement's sizes carefully, as some ranges have changed.

The same size doesn't always give the same heat, either. Choose a new radiator by the heat the room needs: our guide to what size radiator you need shows how to work it out.

Swapping a single panel for a double is not always a straight swap, because a double is deeper. Our single vs double panel radiator guide has the checks.

If you have a heat pump, ask your installer first. Heat pumps usually run at lower water temperatures, so each radiator gives out less heat.

Check your wall can take the weight

A radiator full of water is heavy, and the brackets carry all of it. Stelrad says many of its radiators weigh more than 25kg. So check the wall before you choose.

• Solid brick or block walls can take most radiators. Stelrad says its cast iron column radiators must go on a solid wall.
• Plasterboard (stud) walls need care when hanging or mounting a radiator. To hang a radiator on a plasterboard wall, Stelrad says it must hang from the studs: the pieces of timber the board is fixed to. So the studs may limit the size or shape you can fit. If a bracket falls between them, ask a builder or heating engineer about adding timber support, sized and fixed for the radiator's full weight. Ordinary wall plugs won't do. Eastbrook says the plugs and screws it supplies "are suitable for solid brick walls, not plasterboard walls".
• Heavy designer radiators need their maker's advice. DuraTherm says some of its tall designer radiators must go on a solid wall, and offers floor legs for plasterboard walls instead.

Fix any cracked or crumbling plaster before you start. Wall plugs and screws aren't always in the box: Stelrad doesn't supply them with its panel radiators, so buy fixings that suit your wall. For a designer radiator installation, our designer radiator buying guide covers weight, pipe centres and valves.

What you'll need

These are the tools and parts needed for a like-for-like radiator replacement:

• The new radiator, with its brackets, bleed screw (air vent) and blanking plug. Stelrad, for example, supplies these in the box.
• Wall fixings that suit your wall.
• Two adjustable spanners: one to hold each valve still while the other turns its nut. An adjustable pipe wrench can do the holding if a spanner won't grip.
• A radiator key for the bleed screw. Some bleed screws take a flat-head screwdriver instead.
• A lockshield key, small spanner or Allen key, to close the lockshield valve.
• The right tool for your valve tails (check the valve maker's instructions), to move them from the old radiator to the new one.
• PTFE tape, if your valve's instructions tell you to use it.
• A drip tray, plus a bucket or bowls. Stelrad suggests a paint roller tray.
• Old towels and dust sheets. The water can be dirty.
• A tape measure, pencil and spirit level.
• A drill, the right bits and a detector for pipes and cables.
• A screwdriver or drill driver for the bracket screws.
• Rags to plug the old radiator, and a helper for lifting.
• Your boiler manual, for its pressure and how to top it up.

Plan the day. Your heating is off while the radiator is out, so start early and don't begin a job you may not finish in a cold snap. Keep the old radiator until the new one is hung and filled. If the new one doesn't line up, you can hang the old one back.

How to remove a radiator, step by step

To remove and replace a radiator, you shut it off, drain it at one valve nut and lift it off.

Step 1: Turn the heating off and let it cool

Switch the heating off at the boiler or its controls. Then let the pipes and radiator cool: Stelrad suggests waiting at least an hour. Hot water from a radiator can scald.

Put dust sheets and old towels down under the radiator and its valves.

Step 2: Close both radiator valves

Most radiators have a valve at each end. Close both to shut the radiator off from the rest of your heating.

• Thermostatic valve (TRV): check its instructions, because makers differ. On a Danfoss RAS-C2, you turn the head past the frost setting to 0, which shuts it off. Drayton says never to close its TRV4 with the head for radiator removal. You unscrew the head and close the valve with a manual cap instead. Either way, the frost setting isn't off, Vaillant warns.
• Manual valve: turn it clockwise until it stops.
• Lockshield valve: this is the valve with a plain plastic cap, which sets the flow. Pull or unscrew the cap. Then turn the spindle clockwise with a lockshield key, spanner or Allen key until it stops. Count the turns and write them down, so you can set the new radiator the same way.

Not every TRV has a shut-off setting, Stelrad says. If yours has none and you don't have its manual cap, or a valve won't close, stop here and call a heating engineer.

Step 3: Drain the radiator at the valve nut

The water comes out at the union nut, where one valve joins the radiator. Don't touch the nut where the valve joins the pipe. This diagram shows which nut is which.

Text version:

• Bleed screw: at a top corner. It lets air in while you drain the radiator, and lets air (then water) out while you fill or bleed it.
• Blanking plug: fills the other top corner.
• Valve tail: screws into each bottom corner of the radiator.
• Union nut: joins the valve to the tail. Undo it to drain and remove the radiator.
• Valve: stays on the pipe, closed.
• Pipe nut: joins the valve to the pipe. Leave it alone.

To drain the radiator:

1. Slide the tray under the valve and pack towels round it.
2. Hold the valve body still with one spanner, so you don't twist the pipe.
3. Loosen the union nut with the other spanner. Water will start to run out.
4. Open the bleed screw a little, about a quarter turn, with your radiator key. It lets air in at the top, so the water drains out faster at the bottom.
5. If the tray fills up, close the bleed screw and nip the union nut back up to slow the flow while you empty it. Then carry on.

Keep going until the water stops. It may be dark and dirty: Vaillant says older systems can have murky water, so keep it off carpets.

If the flow doesn't slow down and stop, a valve may be letting water through. Close the bleed screw, do the union nut back up and call a heating engineer before you take the radiator off.

Step 4: Undo the other side and lift the radiator off

Close the bleed screw and undo the first union nut fully. Move the tray to the other valve, hold the valve still, and undo that union nut too.

With a helper, lift the radiator up off its brackets. Ease it away gently, without bending the pipes. If it catches on the valves, don't force it. Ask a heating engineer to look.

There'll still be water inside, so tilt it over the tray to drain the rest. Then plug the open connections with rag or tissue, as Stelrad suggests. Stand the radiator on old towels or a dust sheet, because the water left in it may be dirty.

Check the two valves left on the pipes. Any drips should soon stop. If water keeps coming from either one, it isn't shutting off. Hang the old radiator back on, do both nuts up and call a heating engineer.

How to fit a radiator, step by step

Now for installing the new radiator. Take your time over the brackets: they decide whether the radiator meets the valves.

Step 5: Take off the old brackets and mark the new ones

Your new radiator probably won't fit the old brackets. Vaillant calls it "highly unlikely", so unscrew them and fill the old holes.

Mark the new bracket positions from the valves, not from the old holes:

1. Use every bracket and fixing position the new radiator's instructions give for your model. Stelrad, for example, adds a third bracket on its longest panel radiators.
2. Set the height from your valves, so the radiator's bottom connections will sit level with the valve nuts.
3. Mark the holes and check the marks with a spirit level.

Reflective foil behind a radiator on an outside wall is optional. It is meant to cut the heat lost through the wall. If you want it, stick it up now, before the radiator goes on, and follow the foil maker's instructions.

Step 6: Check for pipes and cables, then fix the brackets

Check what's behind the wall before you drill. A detector helps, but it can miss things:

• Scan with the old radiator off the wall. Bosch says its wall detector can't reliably find things near solid metal, such as a radiator. It can also miss a cable that's too deep, or one that isn't carrying power.
• Scan for pipes as well as cables, as Vaillant advises.

Then read this box before you pick up the drill.

Safety before you drill: Check for hidden pipes and cables first. The UK wiring rules, BS 7671, say cables buried less than 50mm deep without other protection should run within 150mm of the top of a wall or of a corner. Or they should run straight up, down or across from the switch, socket or other fitting they serve. Since Amendment 4 (2026), these zones can carry cables from other circuits too. In a thin wall, a zone can carry on through to the other side. Older or altered homes can have cables elsewhere, and protected cables can run outside the zones.

Scan the spot as your detector's instructions say. A clear scan isn't proof: detectors can miss cables that aren't carrying power, and damp walls can fool them.

So before you drill, have a registered electrician find every circuit that could run behind the wall, then isolate it, lock it off and prove it dead with proper test equipment. That is what HSE's safe working guidance (HSG85) asks for. Don't try to test a circuit yourself unless you're competent to. A detector can't prove a circuit is dead. Where you can, use a cordless drill as well, as Electrical Safety First advises.

Pipes don't follow the cable zones, so take care near them too. If you're unsure where pipes run, ask a plumber or heating engineer.

Then drill, and fix the brackets with fixings that suit your wall. Check they're firm before the radiator goes on.

Step 7: Move the valve tails and fit the bleed screw

The valve tails screw into the radiator, and the union nuts tighten onto them. Check your tails suit the new radiator's connections. Stelrad calls a half-inch tail the industry standard, but not every radiator uses one.

Unscrew the tails from the old radiator with the right tool (Vaillant's kit list for this job includes a large Allen key). Clean them and screw them into the new one. If they don't suit it, or one is damaged or stuck, ask a heating engineer.

Fit the new radiator's bleed screw and blanking plug in its top corners too. It's easier to do all this with the radiator on the floor, before you hang it.

Seal only where the instructions say. Tape and jointing compound aren't for every joint, and makers differ:

Part	Tape or sealant?
Valve tail thread, into the radiator	Only as the valve's instructions say. Drayton, for example, says 4 to 6 layers of PTFE tape
Bleed screw and blanking plug	Only as the radiator's instructions say. Stelrad's need "No tape or seal required", but Eastbrook says to tape its bleed valve
Union nut, valve to tail	None, unless the valve's instructions say so
Pipe nut, valve to pipe	Leave it alone in a like-for-like swap

Step 8: Hang the radiator and plumb it in

With your helper, lift the radiator onto its brackets. Check it sits level, and that both tails line up with the valve nuts.

Plumbing a radiator in, like for like, comes down to connecting those two union nuts. To connect each side, hold the valve body still with one spanner and tighten its union nut with the other. Make them firm, but don't force them.

Don't open either valve until the radiator is hung and both nuts are done up. Opening a valve to a radiator that isn't connected empties your heating onto the floor.

Step 9: Fill the radiator slowly and bleed out the air

These steps follow Stelrad's filling instructions. Keep the heating off and the water cool.

On a sealed system, check the gauge shows the cold pressure your boiler manual gives. Keep it there while the radiator fills: if it drops below that, top up as the manual says. If you can't keep the pressure up, close the filling loop and the lockshield, then call a heating engineer.

1. Open the bleed screw about a quarter turn, with a cloth held under it.
2. Open the lockshield valve slowly. You'll hear the radiator filling and air hissing out of the bleed screw. The gurgling stops as it fills.
3. Watch the bleed screw. It spits air and water at first. Close it as soon as water runs out steadily, with no more air.
4. Open both valves. Open the lockshield by the number of turns you counted, from fully closed. Set the TRV or manual valve back to its old setting. If you fitted a manual cap, refit the TRV head as its maker's instructions say, then set it.

On a sealed system, the pressure drops as the radiator fills, so keep an eye on the gauge throughout.

Text version:

1. Hang the radiator and do up both nuts, with both valves still closed.
2. Open the bleed screw about a quarter turn, with the heating off.
3. Open the lockshield slowly. On a sealed system, keep the pressure up.
4. Close the bleed screw as soon as water runs out with no air.
5. Open both valves, with the lockshield at your counted turns from closed.
6. Check the pressure and every joint. On a sealed system, top up only if the gauge reads below the cold pressure your manual gives.

Step 10: Check the pressure and look for leaks

On a sealed system, check the boiler gauge while the system is cool. Worcester Bosch says it should read between 1 and 1.5 bar. Makers vary, so check your manual. If it's low, top it up exactly as your boiler's instructions say, then close the filling loop fully.

On an open-vented system, the tank in the loft refills the heating by itself.

Next, dry each nut and hold kitchen roll round it to check for drips. Turn the heating on, and check again once the radiator is hot.

If a nut weeps, switch the heating off and let it cool. Then hold the valve body still and tighten the nut gently. If it still leaks, call a heating engineer.

Check the nuts again the next day, once the heating has been on and off. On a sealed system, read the gauge cold each day for a few days, because it reads higher when the system is hot. If the cold reading keeps falling after the air is out, ask a heating engineer to find out why.

Check that the radiator heats evenly all over. A trickling noise, or a cold patch at the top, can mean there's still air in it, Stelrad says. Once it has cooled, bleed it with the heating off, then check the pressure again.

If the pressure keeps dropping, don't keep topping it up, as it may mean a leak. Call a heating engineer, or a Gas Safe registered engineer if the problem is in a gas boiler.

Step 11: Top up the inhibitor

Inhibitor is a chemical in your heating water that slows the corrosion that makes sludge. When you drain a radiator, fresh water replaces the water you lost, so the inhibitor gets diluted. Stelrad says inhibitor is "largely lost whenever the system is drained for a repair or a new radiator, so it needs re-dosing after that work". Worcester Bosch says to check its level sooner if the system has lost water.

Add it as the inhibitor maker's instructions say. Sentinel, for example, says to add its X100 inhibitor through the feed and expansion tank on an open-vented system. On a full sealed system, it says to inject it with its dosing vessel, through the filling loop or another access point. Or ask a heating engineer to test and top it up soon after the swap, rather than at the next service.

If your new radiator is aluminium, check your inhibitor suits it. Eastbrook says it must suit aluminium radiators and not be nitrate based.

Good to know: Was your old radiator cold at the bottom, or the water black? Those can be signs of sludge. Ask a heating engineer about cleaning the system, or the sludge can settle in your new radiator. Our guide to a power flush before new radiators explains the options. Stelrad's warranty doesn't cover pinholes caused by a system that wasn't cleaned and protected.

Fitting a new radiator to existing pipes: what if it won't fit?

If you're fitting a replacement radiator and its connections don't meet your valves, don't force the pipes to reach. You have two choices:

• Choose a radiator that matches. Compare its listed pipe centres and connection height with your measurements.
• Have the pipes moved. Installing new radiator pipes is a job for a heating engineer or plumber. So is moving a radiator, or adding a radiator to an existing system.

Our guide on how to choose a radiator covers output, type, size and fit, so you can pick one that lines up first time.

Radiator questions people ask

Is it easy to change a radiator?

For a like-for-like swap, it's manageable if you're handy and careful: changing a radiator is more fiddly than hard. How easy it is to replace or install a radiator depends on what you find. If the pipes don't line up, the valves won't shut off or the wall is plasterboard, a heating engineer is the better route.

Who fits radiators?

A plumber or heating engineer, if you'd rather have new radiators fitted for you. Costs vary with your area and with whether the pipes need to move, so ask two or three local engineers for a written quote. The HSE says you don't need to be Gas Safe registered to fit a radiator. You do for any work on a gas boiler, including the final connection of the pipes to it.

Do you need to drain the system to change a radiator?

No, not for a like-for-like swap. You only drain the radiator you're changing, because its two valves hold back the rest of the water. Changing the valves themselves is different. Stelrad says fitting a new TRV means isolating and draining that part of the system. Our guide to changing a radiator valve shows what that involves.

How do you put a radiator back on the wall after decorating?

Putting a radiator back on after decorating uses the same steps, from Step 8 onwards. Hang it on its old brackets, reconnect both union nuts, and refill it as Step 9 shows. Then check the pressure and the joints.

When should you replace a radiator?

When it's past saving, or when it never heated the room properly. Common reasons are:

• Pinholes, or lasting corrosion inside. These mean it's time.
• Cold patches that don't clear. A radiator that's just cold in places may only need fixing first. Cold at the top is usually air, and cold at the bottom is usually sludge. No heat at all while the other radiators work is usually a closed or stuck valve. Our guide to checking and maintaining radiators shows how to fix a radiator's common problems. If those checks don't solve the problem, ask a heating engineer to find the cause before replacing the radiator.
• Too little heat for the room. A radiator that was never big enough won't improve with age.
• Age and condition. Stelrad says a well-maintained steel panel radiator typically lasts 15 to 20 years, and many last longer. Age alone needn't mean replacement.
• A new look or a new home. If you're changing style, check the new radiator's output and pipe centres, not just how it looks.

Measure first, then choose

A like-for-like swap is only as simple as the fit. Measure your pipes and wall before you buy, and the rest of the job follows.

Ready to choose? Browse Plumbworld's radiators, and finish the job neatly with radiator pipe sleeves and collars to hide the bare pipes.

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