How To Replace A Radiator
Swapping an old radiator for a new one the same size is a tidy DIY job once you know the order to do it in.
The short answer
To replace a radiator, turn off the heating and close both radiator valves, then loosen the valve nuts to drain the old radiator into a tray and lift it off its brackets. Fit new brackets, wrap the new radiator tails in PTFE tape, hang it and reconnect the valves. Open the valves, bleed out the air and check every joint for leaks.
Replacing a radiator with a new one of the same size is well within reach for most DIYers, because the pipes stay where they are and you're just unscrewing one and hanging another. It gets harder when the new radiator is a different width, as the pipework under the floor has to move to meet it.
The steps below are for a like-for-like swap. If you haven't settled on the new one yet, our guide to choosing the right radiator size for a room helps you work out the heat output you need first.
Check The Wall Before You Start
With the old radiator off, you get a rare look at the wall behind it. Check for cracked or crumbling plaster around the old brackets and repair it before the new one goes up, using a good wall filler for cracks and holes for small areas or fresh plaster for anything bigger. It's also the easiest time to paint that patch of wall, since you won't be able to reach it once the new radiator is hung.
Fitting A Larger Or Smaller Radiator
If the new radiator is wider or narrower than the old one, the pipes have to be extended or cut back so they line up with the new valves. That means lifting floorboards, rerouting pipe and sometimes notching joists, which is a job for a plumber unless you're confident with soldered or push-fit joints.
The photos below are from one of our own swaps, where the new radiator was much larger than the old one. We had the pipework altered under the floor before the new carpet went down, which saved lifting it again later.
What You'll Need
- Replacement radiator with new brackets
- New thermostatic radiator valve if you're upgrading the old one
- Two adjustable spanners
- Radiator bleed key
- Drill with masonry drill bits for brick and block walls
- Wall plugs, screws, spirit level and pencil
- PTFE tape
- A shallow tray, bucket and old towels
How To Replace A Radiator Step By Step
1. Turn Off The Heating And Isolate The Radiator
Switch the heating off and let the radiator cool. Close the valves at both ends. A manual valve or TRV turns clockwise to off, while the lockshield valve at the other end sits under a plastic cap and needs a spanner.
Count the turns as you close the lockshield and write the number down. Opening it the same amount on the new radiator keeps the system balanced, so every room heats evenly.
2. Drain The Old Radiator
Put towels and a shallow tray under one valve. Hold the valve body steady with one spanner so the pipe doesn't twist, then loosen the swivel nut between the valve and the radiator with the other.
Water starts to trickle out. Open the bleed valve at the top of the radiator a little to let air in, and the flow speeds up. Empty the tray as it fills and tighten the nut whenever you need a break.
3. Lift The Radiator Off
Once the flow has stopped, undo both swivel nuts completely and lift the radiator up and off its brackets. Tip it so the last of the water runs out of one corner into the tray. There's always more left inside than you'd expect, and it's black and stains carpets. Get a second pair of hands for a big one, because they're heavier than they look.
4. Fit The New Brackets
New radiators come with their own brackets, and these rarely line up with the old holes. Unscrew the old brackets, then measure and mark the new positions so the valve connections sit directly above the pipes. Drill and plug the wall, check the brackets are level and screw them on firmly.
5. Fit The Valve Tails To The New Radiator
Wrap PTFE tape around the threads of the radiator tails and screw them into the bottom corners of the new radiator, along with the bleed valve and blanking plug at the top. If you're reusing the old valves, clean up the olives and threads with wire wool first so they seal properly.
6. Hang The New Radiator
Lift the radiator onto the brackets and check it sits level and square. Line up the tails with the valves and make sure there's no strain on the pipes.
7. Reconnect The Valves And Bleed
Tighten the swivel nuts onto the tails, again holding the valve body with a second spanner. Open the TRV or manual valve fully, then open the lockshield by the number of turns you noted earlier. Open the bleed valve until water rather than air comes out, then close it.
8. Check For Leaks And Repressurise
Wipe every joint dry and check it with a tissue for weeps. On a combi or system boiler, the pressure will have dropped while the radiator filled, so top it up following our guide to repressurising your boiler. Turn the heating on, let the new radiator warm through, then bleed it once more and check the joints again.
When To Drain The Whole System
Isolating the radiator at its valves is enough for most swaps. If one of the valves won't close fully, the valves need replacing or the pipework is changing, you'll need to drain the system down first, which our guide to draining a central heating system covers in full.
What Affects The Cost Of Replacing A Radiator
If you'd rather have a plumber do it, the price depends on how much work is involved more than the radiator itself. A like-for-like swap on the same pipes is the quickest and cheapest job. Moving to a different size means altering the pipes under the floor, and moving the radiator to another wall adds a longer pipe run and more floor lifting.
Location, access and any surprises such as seized valves or corroded pipes affect the final bill too. Having several radiators replaced on one visit saves money, as the plumber only drains and refills the system once.
Repair, Repaint Or Replace
A radiator that's cold at the top only needs bleeding, and one with tired paintwork can be freshened up with a heat-resistant radiator paint. If it's cold at the bottom, rusting through or simply too small for the room, a new one is the better fix, and as long as it's the same size, it's a job you can tackle yourself.
What People Also Ask Us
Can I replace a radiator without draining the system?
Yes, you can replace a radiator without draining the whole system if both radiator valves close off fully. Isolate the radiator, drain just that one into a tray by loosening a valve nut, and swap it over. If a valve leaks when closed or needs changing too, drain the system down first.
Can I replace a radiator with a bigger one?
You can replace a radiator with a bigger one, but the pipes need to be altered so they reach the new valve positions. That means lifting floorboards and extending or rerouting the pipework, which most people leave to a plumber. Check the new radiator's heat output suits the room, as a bigger one isn't always needed.
Do new radiators come with valves?
Most new radiators come with brackets, a bleed valve and a blanking plug, but not the valves or tails. You can reuse your existing valves if they're in good condition and turn off fully. Fitting new thermostatic radiator valves at the same time is a cheap upgrade that gives better control of each room.
Why is my new radiator cold at the bottom?
A new radiator that's cold at the bottom has sludge from the old system settled in it, or the lockshield valve isn't open enough. Check the lockshield is open to the number of turns you noted. If it is, the system needs flushing, and a magnetic filter fitted afterwards stops the sludge building up again.
Why do I need to count the turns on the lockshield valve?
The lockshield sets how much hot water each radiator gets, so opening it by the same number of turns on the new one keeps the system balanced and every room heating evenly. Jot the number down as you close it, because it's easy to forget by the time the new radiator is on the wall.
Why don't the new radiator brackets line up with the old holes?
Each radiator comes with its own brackets, set to suit that radiator, so they rarely match the old holes. What matters is that the valve connections on the new radiator end up directly above the pipes. Mark the bracket positions from there, then drill, plug and level them before screwing them home.
Is it worth painting the wall before hanging the new radiator?
Yes. Once the new radiator is hung you can't reach that patch of wall, so paint it while it's bare. Look over the plaster around the old brackets first, and fill small cracks or re-plaster anything crumbling before the paint goes on.
Can I reuse my old radiator valves on the new radiator?
You can reuse them if they close fully and are in good condition. Clean up the olives and threads with wire wool first so they seal properly. If a valve won't close fully, or you want a thermostatic valve instead, fit a new one, and you'll need to drain the whole system down.
Richard has spent years renovating properties and turning them into rentals and Airbnbs. Like a lot of people he started out as a beginner, and these days there isn't much DIY he won't take on.