For a straightforward like-for-like swap, a competent plumber will usually have a new radiator on the wall and working within one to two hours. Fit a radiator in a new position, or add one to an older system, and you could be looking at half a day or more. Here is what actually determines the time, based on the jobs we see day in, day out around Wigston and south Leicestershire.
The single biggest factor is whether the new radiator matches the old one. If the pipe centres line up, the job is mostly mechanical: drain down or freeze the pipes, remove the old unit, hang the new one, connect, refill and bleed. If the pipework has to move, everything takes longer because floors or plaster may need opening up.
These ranges assume reasonable access and a system in decent condition. Victorian terraces with pipes buried in solid floors, or radiators tucked behind boxed-in pipework, sit at the top end of each range.
Most swaps start with isolating or draining the system. On a sealed combi system this is quick; on an older open-vented system with a tank in the loft, draining and refilling alone can add 45 minutes to an hour. Some plumbers use pipe freezing kits to avoid a full drain down on simple swaps, which saves time but is not always suitable.
Once the old radiator is off, the wall often needs attention. Old brackets rarely match new ones, and behind a radiator that has hung there for 20 years you will usually find flaking paint or bare plaster. Ten minutes of filling and a quick coat of paint now is far easier than doing it once the new radiator is up. Then it is a case of fitting the valves, hanging the radiator, refilling, adding inhibitor, and bleeding every radiator in the house to clear airlocks.
Sludge is the big one in older Leicestershire housing stock. If the system water comes out black, fitting a clean new radiator to a dirty system means it will clog early. A chemical flush adds a couple of hours; a full powerflush is typically a day on its own. It is worth doing, but it changes the scope of the job.
Pipework in solid floors, microbore pipe (the narrow 8mm or 10mm pipe common in 1970s and 80s builds), seized valves that shear off when touched, and plasterboard walls that need extra fixings for a heavy cast iron or vertical radiator can each add an hour or more. A good plumber will spot most of these at the quoting stage rather than on the day.
Clear a working area of about a metre around the radiator and lift anything off the floor nearby, as a small amount of water escaping during removal is normal even with careful draining. If your stopcock or drain-off valve is buried behind stored boxes, dig it out beforehand.
If you know where your boiler, filling loop and any loft tank are, tell the plumber at the start. On a straightforward swap booked for the morning, your heating should be back on the same afternoon. We always aim to leave a system refilled, balanced and dosed with inhibitor before we leave, and it is reasonable to expect that from anyone doing the work.
Heating is off while the system is drained or isolated, usually a few hours at most for a swap. On a combi boiler your hot water is often unaffected, as it is heated separately from the radiators.
A confident DIYer can manage a like-for-like swap, but you take on the risk of leaks, airlocks and forgetting inhibitor, which shortens the life of the whole system. Anything involving moving pipework or a system flush is best left to a plumber.
Labour for a simple swap is commonly in the region of £100 to £200, with the radiator and valves on top, though it depends on access and pipework. Relocations and flushes cost more, so ask for a fixed quote after the plumber has seen the job or clear photos of it.