Remove and replace radiators that aren’t working properly and, as well as saving you energy, it will ensure that your home is being heated efficiently.
Replacing a new radiator isn’t too difficult a task, but do be sure to follow our instructions to avoid any unnecessary mess as well as any impact to the system.
Check the visible condition of the wall where the radiator will be hung. If there are any cracks or crumbling plaster it’s worth considering making repairs before you fit your new radiator.
If the wall is constructed from solid masonry – bricks or blocks cemented together with mortar – you’ll have the greatest choice of replacement radiators. These are strong solid walls and so, there will be few limitations on the size and style of radiator you can choose. With the right fixings, larger radiators can be placed on any part of the wall.
If the wall is constructed from plasterboard with a hollow space behind (a drywall or studwork wall), you’ll need to find out where the studs or noggings run – these are the vertical or horizontal pieces of timber that the plasterboard is attached to. A stud detector will help you find these. The studs are the strongest part of your wall, and so your radiator will need to be hung from these. Depending on their location, you may be limited on the shape or size of radiator you can use in the space.
The easiest way to replace a radiator is to choose a new one with identical pipe centres. However, if your new radiator is a different width from the old one, you’ll need to drain the system and make alterations to the pipework. Doing this is quite a straightforward task – modern plumbing fittings are very easy to work with – and will mean you can choose from a much wider range of designer radiators. Drain the system before you begin and remove flooring and skirting as necessary in order to gain access to the pipework.
Turn off the heating and isolate the radiator by closing off the valve at either end. Simply turn the manual valve clockwise until it won’t turn any further (if you have a thermostatic valve, turn this through to zero or the off position). If you have a lockshield valve at the other end, pull off the plastic shield and turn the square shaft clockwise with an adjustable spanner. Count and note the number of turns so that you can reset the new radiator at the same flow rate.
Place a tray beneath the valve to catch the water as it drains out. With both valves turned off, use an adjustable spanner to loosen one of the cap nuts connecting the valve to the radiator. You may need to hold the valve body with a second spanner or pipe wrench to prevent it turning and buckling the pipe.
Open the bleed valve at the top of the radiator and loosen the cap nut. When the tray is almost full, re-tighten the cap nut and empty the tray into a bucket. Be ready with cloths to mop up any spillage – the water may be filthy, especially if you have an older system. Repeat until all the water has drained out, and then disconnect the other valve.
Lift the radiator from its brackets and tilt to drain any remaining water. Get your helper to stuff an old rag or tissue into the outlet at the other end to stop it leaking. If the existing brackets don’t suit the new radiator, unscrew them and fit those supplied with the new radiator. Before drilling into the wall, be sure you’ve checked what’s behind it with a pipe, cable and stud detector (also known as a multi-purpose digital detector). They’re simple to use and will let you know if there are any pipes, cables or studs where you’re planning to work. Simply run it over the surface of the area and it will tell you where hazards lie.
Fitting reflective foil behind your radiator can reduce your heating costs by reflecting heat back into the room that would otherwise be lost through the wall. It is particularly effective for radiators on the colder outside walls.
Remove the valve connectors from the old radiator, using an adjustable wrench or large allen key. Clean the threads with wire wool and wind PTFE tape around the threads about five times to ensure a good seal. Screw the connectors into the new radiator, making sure they are tightened fully, and then hang the radiator. Connect the valves and reset them, allowing the water to enter. You’ll need to open the bleed valve about half a turn so that air can escape; be sure to close it when water starts to appear.
Thermostatic radiator valves (TRVs) let you control your heating system more efficiently. The position of your radiators can also make a big difference to how effective they are. For example, if they're blocked behind big pieces of furniture, they'll heat a room much less efficiently. If you want to change the layout of your room, look at repositioning your radiators.
By simply turning down your room thermostat by one degree could reduce your heating bills by about £85 a year. Fitting a room thermostat alongside thermostatic radiator valves could reduce your heating bills by between £80 and £165 per year.
Source: Energy Saving Trust, checked 2015.
All wet central heating systems will be provided with at least one drain cock, a valve that let’s you drain out water, to allow the system to be emptied for maintenance or repairs. Usually, this will be in the return pipe close to the boiler. However, where a solid ground floor prevents pipes from being run below it, the pipes will drop down from the ceiling to supply ground floor radiators. These sections of pipework will remain full of water when the system is drained from the boiler drain cock and will have their own drain cocks, allowing them to be emptied separately.
When refilling the system, make sure all drain cocks and radiator bleed valves are closed before restoring the water supply to the feed-and-expansion cistern in the loft. As water flows into the system, air will become trapped in the radiators, so bleed each by opening the bleed valve about half a turn, starting at the bottom of the house and working upward. Before turning the pump back on, bleed this too.
Before draining the system, switch off the boiler, but allow the boiler circulation pump to run for 10 minutes to cool the water. Then turn off the pump and close the stop valve in the pipe supplying the feed-and-expansion cistern – this will prevent the system filling up with water. If there is no valve, place a batten or narrow piece of wood across the top of the cistern and using a piece of string, tie the ball valve arm to it to prevent the valve from opening and letting water flow into the cistern. Push one end of the hose onto the outlet of the drain cock. Run the hose to an outdoor drain.
Use an adjustable wrench to open the drain cock, but don’t remove the square valve shank completely. When the feed-and-expansion cistern has emptied, work down through the house, opening radiator bleed valves to release any remaining water trapped in the radiators.
It’s best to completely flush the whole system and add a central heating protector (corrosion inhibitor) even if you’ve only replaced one radiator. This helps prevent the breakdown of your heating system internally – having water flowing constantly against metal causes it to rust and this creates sludge in your system and stops it working properly. Adding a corrosion inhibitor can help limit this damage.
Corrosion inhibitor should be added to a system when it’s installed, but it can also be added later if required. Make sure you buy a product compatible with the materials your boiler, pipes and radiators are made of; if in doubt, consult a qualified plumber.
If replacing any radiators, you will lose corrosion inhibitor and so the system will not be fully protected against the damaging effects of corrosion and sludge. Do ensure that the system is properly topped up. Depending on the size of the house and number of radiators, more than one bottle of inhibitor may be required. As always, refer to the manufacturer’s instructions.
With an older installation, it’s a good idea to flush the system first to remove any build-up of corrosion sludge, which can eventually cause the pump to fail. Turn off the heating and allow the water to cool, then drain the system completely. Refill and drain again. Carry on in this way until the water runs clear.
Partially fill the system, pour the correct quantity of corrosion inhibitor into the feed-and-expansion cistern (5 litres should be enough for most domestic systems, but check the manufacturer’s instructions) before allowing the system to fill completely. Turning the boiler and pump back on will cause the corrosion inhibitor to be mixed thoroughly with the water.
Alternatively, you could use a product that’s designed to be injected from a cartridge straight into one of the radiators. This removes the need to drain down the system.