Boiler Repair London — Gas Safe Registered

Every engineer we send for gas work carries a Gas Safe ID card. You can check any gas engineer's registration at gassaferegister.co.uk using the unique licence number on the card. It's worth doing — it takes 30 seconds and confirms the engineer is qualified for the work. You can also check which types of gas work they're registered to carry out (natural gas, LPG, commercial etc.).

A useful rule of thumb: if the repair cost exceeds 50% of what a new equivalent boiler would cost installed, replacement is usually the better financial decision — especially if the boiler is over 10 years old. We'll tell you the repair cost and the replacement cost on the same visit, with no obligation to proceed with either. If your boiler is under warranty, we'll check whether the fault might be covered before quoting for repair.

We work with all major UK brands: Worcester Bosch, Vaillant, Ideal, Baxi, Glow-Worm, Potterton, Ariston and Alpha. We carry the most common parts for Worcester Bosch and Vaillant (the two most common in London) on our vans — diverter valves, expansion vessels, PCBs for common models, pilot assemblies and pressure sensors. For less common brands or older models, parts may need ordering, but this is typically a 24-hour wait.

Recurring pressure loss always means water is leaving the system somewhere. The most common sources: a leaking radiator valve (particularly the plastic wheelhead on older TRVs), a pinhole in a radiator panel, a failed pressure relief valve discharge, or a leaking expansion vessel diaphragm (which allows water into the vessel, displacing the air and causing the PRV to discharge repeatedly). We can pressure-test the system to locate the source. See our guide on boiler pressure loss for more detail.

Technically optional for homeowners — there's no legal requirement for private homeowners to service a domestic boiler annually. In practice, it's required by most boiler warranties (skipping a service voids warranty cover on many models), required by most boiler breakdown insurance policies, and strongly recommended from a safety and efficiency standpoint. For landlords, an annual gas safety check (CP12 certificate) is a legal requirement — the boiler is included in that inspection but a CP12 is not the same as a full service.

We can attend any property — whether you own or rent. If you're a tenant and the boiler has broken down, the landlord is legally responsible for repair under Section 11 of the Landlord and Tenant Act. In practice, the quickest resolution is usually to contact your landlord first and give them a reasonable time to respond (24 hours for no heating in winter). If the landlord doesn't respond and there are vulnerable people in the property, you may be able to arrange emergency repair and seek reimbursement — though this is a legal area rather than a plumbing one, and Citizens Advice is a good resource.

F22 on a Vaillant ecoTEC indicates low water pressure — the system pressure has dropped below the minimum operating threshold (typically 0.5 bar). The boiler locks out as a safety measure to prevent the heat exchanger firing dry. The immediate fix is to repressurise the system to 1.0–1.5 bar using the filling loop (usually a silver braided hose beneath the boiler). If the pressure drops again within a few weeks, there is a leak somewhere in the system — at a radiator valve, a pipe joint or the expansion vessel diaphragm — and this needs locating and repairing rather than repeatedly topping up the pressure.

F1 on a Worcester Bosch Greenstar indicates system pressure is too low (below 0.5 bar). The boiler won't fire until pressure is restored. Find the filling loop — typically a silver braided connector with two valves beneath the boiler — and slowly open both valves until the pressure gauge reads 1.0–1.5 bar, then close both valves. If you have to do this more than once every few months, you have a slow system leak and should book an engineer to find it. Repeated refilling without finding the source leads to corrosion from the oxygen introduced with fresh mains water.

A banging or kettling sound from the boiler almost always indicates limescale build-up on the heat exchanger — particularly common in London's hard-water areas. Scale reduces heat transfer, causing local overheating and steam formation in the waterways, which produces the banging sound. In most cases the heat exchanger can be descaled in situ using a proprietary descaler circulated through the system. If the heat exchanger is cracked (visible with a borescope), replacement is needed. Banging that occurs only on pump start can also indicate trapped air in the system, which is resolved by bleeding the system and checking the pump speed setting.

Yes — turning the boiler off at the power switch is always safe if it's showing an error code. The boiler has already locked out (stopped firing) when an error code is displayed, so switching it off simply removes power from the controls. What you should not do is smell gas near the boiler and then operate any electrical switches — if you smell gas, leave the property, do not use light switches or phones inside, and call the National Gas Emergency Service on 0800 111 999. Error codes indicating ignition failure (F28 on Worcester Bosch and Vaillant) can sometimes be reset once, but if the fault persists after one reset, call an engineer rather than continuing to reset.

First, confirm the boiler is off and cool. Locate the filling loop — a silver braided hose with two isolation valves (usually under the boiler or inside the cabinet). Place a cloth under the loop connections in case of any drips. Slowly open one valve, then the other, watching the pressure gauge on the boiler front. When the needle reaches 1.0–1.5 bar, close both valves — in the same order you opened them. Switch the boiler back on and reset if needed. If your boiler has a built-in filling key (common on Vaillant ecoTEC and some Worcester Greenstar models), the process is similar but uses the integrated key rather than a separate loop.

A gas safety check (producing a CP12 certificate) is a legal inspection that confirms all gas appliances in a property are safe to use. It covers operating pressure, flue integrity, burner combustion and ventilation — and results in a pass or fail per appliance. A boiler service is a maintenance procedure: it includes everything in the safety check plus cleaning the heat exchanger, checking the ignition electrode gap, inspecting the condensate trap, checking inhibitor concentration and replacing any worn seals. A landlord's CP12 does not substitute for an annual service — the service protects the boiler's condition and warranty; the CP12 protects the tenants and the landlord's legal compliance.

It depends on the warranty terms. Worcester Bosch and Vaillant extended warranties (7 or 10 years) typically require repairs to be carried out by the manufacturer's own service network or an approved installer. If you use a third-party engineer — even a Gas Safe registered one — for a warranty repair without manufacturer authorisation, you may void the remaining warranty. Our approach: we check the manufacturer's warranty portal using the boiler serial number before quoting for any repair on a younger boiler. If the fault is likely covered, we tell you to contact the manufacturer rather than pay us. If the warranty is expired or the fault isn't covered, we proceed with the repair.

A two-year-old boiler breaking down is rare but not unheard of, and the cause is almost always installation quality rather than a manufacturing defect. The most common culprits: failure to power-flush the system before installing the new boiler (introducing old sludge and debris into the heat exchanger); incorrect system pressure settings during commissioning; missing or incorrectly sized expansion vessel; poor flue installation creating back-pressure or condensate pooling. A new boiler with a faulty installation can fail within months. We'll diagnose whether the fault is a component failure (potentially warranty-covered) or an installation deficiency — and if it's the latter, we'll document it so you have grounds to approach the original installer.