Central Heating Repair London — Same-Day Engineers

London's water hardness (300mg/l+ calcium carbonate) is among the highest in the country. Limescale forms inside boiler heat exchangers, reducing heat transfer and causing kettling noise. Magnetite sludge — corroded metal particles — accumulates in radiators and pipework, causing cold spots and pump wear. Systems without magnetic filters or chemical inhibitor are particularly vulnerable. Most London systems over 10 years old have significant sludge build-up, and many heating faults that appear electrical or mechanical are actually caused by sludge blocking pump impellers or valves.

We charge £65–£85/hr labour plus a £60 call-out (waived on jobs over 2 hours). Most heating faults are diagnosed and repaired in 1–3 hours. Common repairs: pump replacement £180–£280 inc. parts; zone valve replacement £120–£180 inc. parts; expansion vessel re-pressurisation £85–£120; thermostat replacement £95–£180 depending on type; pressure relief valve replacement £95–£140. Complex faults requiring parts to be sourced — PCB replacement, diverter valve — typically add a day for parts delivery.

If your system has multiple cold radiators, discoloured bleed water (dark brown or black), or the boiler cycles on/off repeatedly, sludge is likely the underlying cause and a repair alone won't resolve it for long. A targeted single-radiator flush (£95–£150) can help if only one radiator is affected. A full power flush (£299–£599 depending on radiator count) clears the sludge system-wide and is usually combined with a magnetic filter installation (£85–£140) to prevent recurrence.

We can give you a provisional diagnosis based on your symptoms — it saves time and helps us bring the right parts. Common patterns: if all radiators are cold but the boiler fires, the pump has usually failed. If one zone is cold, a zone valve is stuck. If radiators are hot at the top but cold at the bottom, sludge has settled in the panel. If the boiler pressure keeps dropping, the expansion vessel needs re-pressurising. Call us and describe your symptoms — we'll narrow it down before the visit.

Most repairs are completed in 1–3 hours. Simple repairs — bleeding radiators, re-pressurising the boiler, replacing a faulty TRV — take under an hour. More complex repairs — zone valve replacement, pump replacement, expansion vessel work — take 1.5–2.5 hours. If a part needs ordering (PCBs, specialist components for older boilers), we typically return the following day with the part already on the van.

Frequent lock-out (boiler fires briefly then cuts out) is usually caused by: low system pressure (check the pressure gauge — should be 1–1.5 bar cold), a blocked condensate pipe (in winter cold snaps), a faulty thermistor or overheat thermostat, or a blocked heat exchanger. If the boiler displays a fault code, that helps narrow it down: Worcester F28 = gas supply issue; F29 = ignition fault; Vaillant F22 = low pressure; F75 = pressure sensor fault. Call us with the fault code if you have one.

Standard home buildings and contents insurance does not cover boiler breakdown or heating system faults — that requires a separate boiler cover policy. However, if a heating fault has caused damage (e.g., a burst radiator valve causing water damage), the resulting damage may be covered under buildings insurance. We can provide a written engineer's report for insurance claims. Some home emergency add-ons do cover callout costs — check your policy documentation.

Yes. We service and repair wet (water-based) underfloor heating systems — manifold faults, thermostat issues, zone valve failures and pump problems. Electric UFH repairs require an electrician rather than a plumber. We also connect UFH systems to new boilers and commission new UFH installations.

We work on all systems, including old gravity-fed conventional boiler systems, back boilers (gas fire with back boiler behind), and older Potterton/Ideal models. Parts availability becomes the main constraint on systems over 20 years old. We always advise honestly if repair isn't economical — a 22-year-old boiler with a failed PCB costing £350+ to repair is usually not worth fixing.

First check: the boiler pressure gauge (should be 1–1.5 bar cold — if below 0.5, re-pressurise via the filling loop before calling). Second: the thermostat settings (ensure it's set above room temperature). Third: the programmer/timer (ensure it's set to ON or HEATING). Fourth: the pilot light (on older boilers — if out, try re-lighting following the boiler manual). If these checks don't resolve it, call us — there's no charge for the phone consultation.