Central Heating Repair in London

A boiler can be running perfectly and your house can still be cold, because the boiler is only the engine. The heat has to travel: through pumps, valves, thermostats, pipework and radiators, and any one of them can quietly sabotage the lot. Our Gas Safe engineers repair the whole central heating system across every London borough: cold radiators brought back to life, seized pumps replaced, motorised valves freed, thermostats and smart controls fitted and fixed, airlocks cleared and systems balanced so every room finally reaches the temperature on the dial. Same-day appointments, fixed quotes before any work starts, and a 12-month guarantee on every repair.

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The circuit

The system around the boiler, and why it fails

Central heating is a circuit, and circuits fail at their weakest point. In London’s housing stock that point is rarely the boiler itself. It is the pump that seized over summer and announces itself on the first cold morning of October. It is the motorised valve stuck halfway, giving you hot water but no heating, or the reverse. It is the thermostat losing its connection so the boiler never hears the house asking for heat, the TRV pin jammed shut behind the sofa, the airlock sitting at the top of a towel rail, or the slow build of sludge that turns the ground-floor radiators lukewarm while upstairs boils. Our engineers diagnose the circuit as a whole, which is why the fix is usually found in one visit rather than three.

What the law requires

Pump

Pushes hot water round the circuit

Motorised valves

Direct heat to radiators or hot water

Thermostat and controls

The brain

TRVs

Per-radiator temperature control

Pipework

The arteries

Radiators

Where the heat finally arrives

Diagnostics

What your radiators are trying to tell you

Symptom

What it usually means

Action

Cold at the top of the radiator

Trapped air; needs bleeding, and if it recurs, air is being drawn in somewhere

Cold at the bottom or middle

Magnetite sludge settling low and blocking flow

Some rooms warm, others cold

Balancing: flow taking the easy route, far rooms starved

No heating but hot water (or reverse)

Classic motorised valve or diverter fault

Banging, tapping or rushing noises

Air, pump speed or pipework expansion

System ignores the thermostat

Controls or wiring fault rather than mechanical

Common repairs

The repairs we carry out every day

Pump replacement

The working heart of the system, and the most common cold-season failure; supplied and fitted.

£200 to £350

Motorised valve

Two-port and three-port valves that direct heat, repaired or replaced with a fixed quote.

£150 to £280

Thermostat & programmer

From rewiring a loose connection to replacing the unit. We will tell you when the honest answer is a £15 battery.

£90 to £200

TRV replacement

Seized or failed radiator valves swapped, often several in one visit.

From £75

Radiator repair & replacement

Leaking, corroded or undersized radiators replaced and balanced in.

Quoted per rad

Balancing & airlock clearing

The whole-house tune that makes every room reach the temperature on the dial.

£95 to £160

Common repairs

Smart controls, fitted properly

Half of London now runs its heating from a phone, and half of those installations were done by whoever was cheapest. We fit and fault-find Hive, Nest, Tado and Honeywell controls, wire them correctly to the boiler they are actually paired with, and set schedules that reflect how the household really lives. Done properly, a smart thermostat trims real money off a gas bill; done badly, it is a £200 ornament that argues with the boiler. If yours has never quite worked since the day it went up, that is a one-visit fix.

HIVE

NEST

TADO

HONEYWELL

The honest bit

When it is not a repair: the sludge conversation

Sometimes the engineer's honest finding is that no single part is broken; the system's water is. Years of magnetite sludge strangle flow, cool radiators from the bottom up and shorten the boiler's life, and no amount of valve replacement fixes dirty water. That is the point where we talk about a power flush, and we will only have that conversation when the evidence supports it. The full picture, including when a flush is genuinely needed and when it is being over-sold, lives on our power flushing page.

Recent work

Recent heating repairs across London

JOB / SW17 / PUMP

A Tooting terrace, SW17: no heating on the first cold Saturday of autumn, seized pump diagnosed on the phone from the symptoms, replaced from van stock before lunch.

JOB / N4 / BALANCING

A Finsbury Park conversion, N4: three cold bedrooms above a boiling ground floor, full system balance and two TRVs, every room within a degree of target by evening.

JOB / E11 / CONTROLS

A Leytonstone semi, E11: a smart thermostat that had never once matched its schedule, rewired and re-paired in forty minutes, gas bill visibly down the following month.

Central heating repair in London, your questions answered

One radiator is cold, do I need an engineer?

Try bleeding it first; cold at the top is usually just air, and it is a five-minute job with a radiator key. Cold at the bottom, or a radiator that needs bleeding constantly, is worth a visit.

Why are my upstairs and downstairs so different?

Usually balancing: the flow favours the shortest route and the far radiators starve. A system balance redistributes it, and it is one of the cheapest whole-house improvements in heating.

Heating works but no hot water, or the reverse. What is that?

The classic motorised valve fault on most London systems, a fixed-price repair our engineers carry parts for.

Can you fix noisy pipes?

Yes. Banging and tapping usually track to air, pump speed or expansion movement, and each has a specific fix rather than a mystery.

Do you repair systems you did not install?

Every day, any age, any London postcode. Older systems get an honest condition report alongside the repair, never a scare story.

Every room warm, this week

Cold rooms, cold radiators, controls that ignore you: one visit usually settles it. Call 020 3000 0000 or request a callback, describe the symptom, and we will tell you before we come out whether it sounds like a five-minute bleed or an engineer’s job.