Leaking Radiator London — Same-Day Repair
We fix radiator valve leaks, TRV faults, pinhole corrosion and full radiator replacements across all 33 London boroughs. Most repairs completed in one visit.
Same day
Available Mon to Sun
From £90
Valve replacement
Stock on van
Common sizes & valves
All 33
London boroughs
Radiator Leaking Right Now? Do This First
These steps take 2 minutes and prevent water damage to floors and ceilings below.
Contain the drip
Place a bowl or towel under the leak immediately. Even a slow drip can cause significant damage to floors and ceilings below, especially in flats.
Isolate the radiator
Turn both radiator valves (one at each end) fully clockwise until they stop. This shuts off water to that radiator only. The rest of your heating continues to work.
Don't try to tighten the main valve body
If the leak is from the valve body (not the gland nut), tightening can make it worse. Turn off the system and call us instead.
If the leak is large or you can't isolate it
Turn off the boiler and call us on 020 7870 3200. We'll get an engineer to you as quickly as we can.
Where Is Your Radiator Leaking? Cause & Cost
Identify the leak location below to understand the likely cause and repair cost.
| Leak location | Likely cause | Temporary DIY | Repair needed | Cost |
|---|---|---|---|---|
| Radiator valve (bottom) | Worn valve packing gland; loose nut | Try tightening the gland nut ¼ turn | Valve replacement | £90 to £180 |
| TRV head / body | Failed TRV body seal or cracked housing | Isolate radiator, no DIY fix | TRV replacement | £110 to £200 |
| Bleed valve (top corner) | Loose or corroded bleed valve | Try tightening bleed valve with bleed key | Bleed valve replacement | £80 to £140 |
| Valve tail (radiator thread) | Degraded thread sealant (PTFE/hemp) | Isolate and call engineer | Re-seal or re-tail | £90 to £160 |
| ⚠Radiator body (pinhole) | Internal corrosion from system sludge | Sealer as temporary only | Radiator replacement | £200 to £450 |
| ⚠Radiator body (seam / weld) | Weld failure on older pressed steel | None, replace immediately | Radiator replacement | £200 to £450 |
⚠ = replace rather than repair. Pinhole and weld leaks indicate widespread corrosion.
Radiator Valve Leaking? Work Out Which Nut Is Wet
A radiator valve has three places it can leak from, and each one has a different fix. Dry the valve with kitchen roll, wrap a dry tissue around each joint in turn and wait a few minutes. Whichever tissue goes damp first is your leak. It works the same on a thermostatic radiator valve (TRV), a manual wheel-head valve or the lockshield valve at the other end.
Leaking from the spindle, just under the cap or TRV head
This is the gland (packing) around the spindle. It is the most common valve leak and often the easiest. With the head or cap off, a small spanner on the gland nut, a quarter turn clockwise while you hold the valve body still with a second spanner, is often enough. If it still weeps, the gland packing or the valve insert needs replacing.
Leaking where the valve meets the radiator
This is the union nut and the radiator tail behind it. A loose union nut can be nipped up, again holding the valve body so you do not twist the pipe. If the leak is from the thread of the tail itself (where it screws into the radiator), the old sealant has failed and the tail has to come out and be re-sealed, which means isolating and partly draining that radiator.
Leaking where the pipe goes into the bottom of the valve
This is a compression joint: a nut squeezing a brass olive onto the pipe. Over-tightening a weeping olive can split it, so a quarter turn is the limit. If that does not stop it, the olive needs replacing. Our guide to a leaking compression fitting explains what goes wrong.
Water from the valve body itself
A crack or corrosion in the brass body cannot be tightened out. Isolate the radiator if the other valve will close, keep a bowl under it and book a valve replacement. Old valves that have not been turned for years sometimes start leaking the first time they are moved, so if yours began dripping right after you adjusted it, this is the likely reason.
Does a leaking radiator valve mean draining the whole system?
Not usually. Tightening a gland or union nut needs no draining at all. Replacing a valve normally needs only the one radiator drained, as long as the valve at the other end still shuts off. Where both valves are seized open, we can freeze the pipe either side of the valve with a pipe-freezing kit so the rest of the system stays full. On a sealed (combi or system boiler) circuit the boiler pressure will drop a little after any valve work, so we bleed the radiator and top the pressure back up before we leave.
If a leak has been dripping for a while, check the boiler gauge. A sealed system that keeps losing pressure is often a small valve leak nobody has spotted yet. Our page on boiler pressure problems covers the other causes.
Radiator Pipe Leaking: Joint, Pipe or Under the Floor
If the valve is dry but there is water on the pipe below it, follow the water upwards. It runs down the pipe and drips from the lowest point, so the wet spot on the carpet is rarely where the leak actually is.
- At a joint on the pipe: a compression joint or a soldered elbow near the floor. Compression joints can usually be re-made with a new olive. A weeping soldered joint has to be cut out and replaced once that section is drained.
- Along the pipe itself: a pinhole in copper, often where the pipe has sat against concrete or been knocked. We cut out the damaged length and join in new pipe.
- Where the pipe comes up through the floor: thin microbore pipe (8 or 10mm) is easily kinked or nicked by floorboard nails. The drip shows at floor level but the damage can be under the boards.
- No drip you can see, but the boiler keeps losing pressure: the leak may be under the floor or in a ceiling void. Look for damp patches on the ceiling below or warm spots on a solid floor, and read our guide to finding a hidden water leak. If it cannot be found by eye, leak detection avoids lifting floors on guesswork.
A leaking radiator pipe under a floor is not something to leave. Even a slow drip into a ceiling below will stain it within days, and in a flat it is your neighbour's ceiling. Turn the boiler off if the pressure is falling fast and call us.
Leaking radiator valve or pipe? We can fix it today.
£95 an hour, with the £60 call-out waived on jobs over 2 hours. Tell us where the water is coming from and we will tell you what to expect before we arrive.
Why London Radiators Corrode Faster
London's very hard water (280 to 320 mg/l) reacts with the steel and iron in radiators to form magnetite (black sludge). This sludge settles in radiators, particularly at the bottom, and accelerates internal corrosion. Radiators in London homes built before 1990 that have never had a power flush are typically showing significant internal corrosion. A central heating inhibitor (such as Fernox F1 or Sentinel X100) slows this process dramatically. We check and top up inhibitor on every radiator call.
Leaking Radiator FAQs: London
Why is my radiator leaking in London?
Radiator leaks in London properties most commonly occur at five points: (1) The radiator valve, either the manual valve or TRV at the bottom of the radiator. The valve body or packing gland can develop leaks, especially in older properties. (2) The bleed valve at the top of the radiator. This small screw valve can corrode or become loose over time. (3) The tail (the threaded fitting that connects the valve to the radiator). If the thread sealant degrades, water seeps at the connection. (4) Pinhole corrosion in the radiator body. London's hard water and system sludge (magnetite) corrode radiators from the inside out, eventually creating tiny holes. (5) The radiator body seam. Older pressed steel radiators develop weld seam failures. Pinhole corrosion is the most common cause in pre-2000 London properties.
How much does it cost to fix a leaking radiator in London?
Leaking radiator repair costs in London: tightening a loose bleed valve or valve packing gland (engineer visit) £80 to £120; radiator valve replacement (manual or lockshield) £90 to £180; TRV (thermostatic radiator valve) replacement £110 to £200; pinhole repair with epoxy/repair putty (temporary) £80 to £150; full radiator replacement (single panel, standard size, supply and fit) £200 to £450; radiator replacement (double panel or designer) £350 to £700. In most cases we can complete a valve or TRV replacement in a single visit of 1 to 2 hours. Radiator replacement takes 2 to 4 hours including draining the system locally.
What should I do immediately if my radiator is leaking?
First, contain the leak: place towels and a bowl under the drip to protect your floor. Second, isolate the radiator if the leak is at the valve: turn both valves (the TRV or manual valve at one end and the lockshield valve at the other end) fully clockwise until they stop. This isolates just that radiator from the system so you can still use the rest of your heating. Third, call us to book a repair. Do not attempt to repair a pressurised system yourself. Even small leaks can worsen quickly if the wrong component is disturbed. If the leak is significant or you cannot isolate it, turn off the boiler and call us on 020 7870 3200.
Can I use radiator leak sealer in my London heating system?
Radiator leak sealers (such as Fernox F4 or Sentinel X100) can temporarily stop minor pinhole leaks without draining the system. They're added to the feed and expansion tank or through a bleed valve and circulate through the system to seal small gaps. However, they are a short-term measure only. They do not fix the underlying corrosion and can clog heat exchangers, pumps and narrow pipework if overused. We recommend using them only to buy time until a proper repair can be done. For persistent or worsening leaks, a powerflush followed by a proper repair is the right solution. We can advise on whether a sealer is appropriate for your specific leak.
My radiator has a pinhole leak. Can it be repaired or does it need replacing?
A single small pinhole in an otherwise intact radiator can sometimes be repaired with a specialist epoxy repair compound (e.g. Sylmasta) as a temporary fix, or with a weld repair if the radiator is accessible. However, pinholes in London radiators are usually a sign of widespread internal corrosion. If you see one, there are typically more developing. For a radiator over 15 years old with a pinhole, replacement is almost always more cost-effective than repair. A new standard double-panel radiator costs £80 to £200 and installation takes 2 to 3 hours. We carry common sizes on the van and can often supply and fit on the same visit.
Can I fix a leaking radiator valve myself?
Sometimes. If the water is coming from the spindle under the cap or TRV head, a quarter turn on the gland nut (holding the valve body still with a second spanner) often stops it. A loose union nut between the valve and the radiator can be nipped up the same way. Stop there: over-tightening a compression olive can split it, and a leak from the valve body or the radiator tail thread needs the valve off. If a quarter turn has not worked, isolate the radiator and book a repair.
Why is the pipe under my radiator leaking?
Usually a compression joint at the valve, a soldered joint near the floor, or a pinhole in the pipe where it has been knocked or sat against concrete. Water runs down the pipe before it drips, so dry everything and trace it upwards. Thin microbore pipe coming up through the floor is easily damaged by floorboard nails. If there is no visible drip but your boiler keeps losing pressure, the leak may be under the floor and needs tracing before anything is lifted.
Do you have to drain the heating to replace a radiator valve?
Normally only the one radiator is drained, provided the valve at the other end still closes. If both valves are seized open we can freeze the pipe either side of the valve so the rest of the system stays full. On a sealed system we bleed the radiator and top the boiler pressure back up before we leave.
Radiator Leaking? Call Now
Same-day repairs. Parts on the van. All 33 London boroughs.
📞 Call 020 7870 3200