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–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 0000 0000. We'll dispatch an engineer to you — average response is 30–60 minutes across London.
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–£180 |
| TRV head / body | Failed TRV body seal or cracked housing | Isolate radiator — no DIY fix | TRV replacement | £110–£200 |
| Bleed valve (top corner) | Loose or corroded bleed valve | Try tightening bleed valve with bleed key | Bleed valve replacement | £80–£140 |
| Valve tail (radiator thread) | Degraded thread sealant (PTFE/hemp) | Isolate and call engineer | Re-seal or re-tail | £90–£160 |
| ⚠Radiator body (pinhole) | Internal corrosion from system sludge | Sealer as temporary only | Radiator replacement | £200–£450 |
| ⚠Radiator body (seam / weld) | Weld failure on older pressed steel | None — replace immediately | Radiator replacement | £200–£450 |
⚠ = replace rather than repair. Pinhole and weld leaks indicate widespread corrosion.
Why London Radiators Corrode Faster
London's very hard water (280–320 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–£120; radiator valve replacement (manual or lockshield) £90–£180; TRV (thermostatic radiator valve) replacement £110–£200; pinhole repair with epoxy/repair putty (temporary) £80–£150; full radiator replacement (single panel, standard size, supply and fit) £200–£450; radiator replacement (double panel or designer) £350–£700. In most cases we can complete a valve or TRV replacement in a single visit of 1–2 hours. Radiator replacement takes 2–4 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 0000 0000.
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–£200 and installation takes 2–3 hours. We carry common sizes on the van and can often supply and fit on the same visit.
Radiator Leaking? Call Now
Same-day repairs. Parts on the van. All 33 London boroughs.
📞 Call 020 0000 0000