Common boiler & heating faults we fix in Surrey & London

The most common causes we find are a faulty PCB (the boiler's control board), a failed gas valve, or worn spark electrodes that stop ignition from working. On a call-out we diagnose the fault first, then talk you through the repair and cost before doing any work — no surprise bills.

Repeated pressure loss is usually down to a failed expansion vessel or a worn pressure relief valve (PRV). We recharge or replace the vessel, fit a new PRV where needed, and repressurise the system so it holds steady rather than dropping again within days.

Yes, this is a common one. A power cut can trip the boiler's electronics or knock out a component like a fan or PCB that was already close to failing. We diagnose, source the part, and get heating and hot water back on the same visit wherever possible.

On boilers over 15–20 years old, parts can be harder to source and we're not able to guarantee the repair the way we would on a newer unit — this is standard practice across the industry, not just us. We'll always explain this upfront and give you the choice between a repair or discussing a straightforward replacement.

We check the boiler's internal components, test gas tightness across the system, and carry out a full safety check. If we find something borderline — like a spark electrode nearing failure or a valve turned off by mistake — we flag it and get your agreement before doing any extra work.

Yes — it's a legal requirement for rented properties, renewed annually. We carry these out alongside a boiler service in a single visit where possible, so you get both done in one call-out.

If you smell gas, call the National Gas Emergency Service immediately on 0800 111 999 (free, 24/7). Turn off the gas supply at the meter if it's safe to do so, open windows to ventilate, and don't use any electrical switches nearby. Once the immediate danger is dealt with, call us — we carry out full tightness tests across the pipework, re-seal or replace faulty connections, and won't leave until the system passes safely.

That's almost always trapped air — an airlock. We bleed the affected radiator and check the wider system for the underlying cause, since airlocks that keep coming back can point to a failing pump or a system needing a proper flush.

Pumps often seize over time, especially in older systems where valves have also worn out. We replace the pump and any seized valves together, then test heating and hot water fully before we leave — this avoids the same fault reoccurring within weeks.

Very often, yes. Most systems use a motorised valve — either a 2-port zone valve or a 3-port valve — to direct hot water from the boiler to either your radiators or your hot water cylinder, depending on what's calling for heat. If that valve's motor or internal mechanism fails, it can get stuck sending water to only one side, leaving you with heating but no hot water, or hot water but cold radiators. We test the valve's motor and internal switching, and in most cases a straightforward valve replacement resolves it completely.

This usually points to a specific component rather than the whole boiler — commonly a diverter valve, flow sensor, or in system boilers, the cylinder's own controls. We isolate exactly which part is at fault before quoting, so you're not paying to replace things that don't need it.

For most homes, yes — better control over heating schedules typically pays for itself in reduced energy use, and it's a straightforward supply-and-install job we can usually do in a single visit alongside a service or repair.

We start with a fixed-price quote covering the full installation (boiler, flue, and any required parts), take a deposit to schedule the work, and complete the balance on completion. You'll always know the full cost upfront — no itemised surprises partway through.

HIU faults are usually specific components — a valve, pump, or control board — rather than the whole unit needing replacement. We're accredited on Danfoss and SAV systems, so we can diagnose and fit like-for-like parts without needing a full unit swap in most cases.

Yes — Talis Heating Solutions is Gas Safe registered (No. 589680), and we hold manufacturer accreditations with Worcester Bosch and Vaillant. You can check any engineer's Gas Safe registration yourself before they start work — we're always happy for customers to ask.

Yes. Once we've diagnosed the fault, we give you a fixed price for the repair before doing any further work — not an estimate that changes once the job's underway. If we find something unexpected once we're inside the system, we'll always explain it and get your agreement before proceeding.

We prioritise no-heat and no-hot-water emergencies, especially for vulnerable occupants or during cold snaps. Call or WhatsApp us and we'll give you a realistic time window rather than a vague "sometime today."

Yes, a call-out fee (from £95+VAT) covers the engineer attending your property. Once on site, an hourly rate applies for diagnosis and any repair work, which we'll confirm before starting. You'll have a fixed price for the repair itself before we go ahead — no open-ended billing.