Boiler Repair or Replace? An Honest Guide for London Homes

A new boiler is one of the biggest plumbing bills a household faces — and 'it's not worth repairing' is sometimes true, sometimes just a sales line. This guide sets out when a repair is genuinely the right call, when replacement actually saves money, and the questions that separate an honest recommendation from an upsell. RenoPlumb London quotes the repair option whenever one exists.

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The short answer

Repair when the fault is a single replaceable component and the heat exchanger is sound. Replace when the heat exchanger has failed, parts are unavailable, the boiler is condemned, or repair bills are arriving yearly. Age alone is not a reason — a well-serviced 12-year-old boiler with one failed pump is a repair, not a replacement.

When repair is the right call

  • A single failed component: pump, fan, diverter valve, thermostat, PCB, ignition
  • The heat exchanger is sound — this is the boiler's most expensive part
  • Spares are still available for the model (we check before advising)
  • The boiler has been serviced regularly and has no history of repeat faults
  • Pressure loss or radiator problems — often a system fault, not the boiler at all

That last point matters: many “boiler problems” are actually system problems — a leak, trapped air, or sludge — where replacing the boiler fixes nothing. See our guide to boilers losing pressure.

When replacement genuinely makes sense

  • Heat exchanger failure — the repair often approaches the cost of a new boiler
  • Parts no longer available for the model
  • The boiler has been condemned as unsafe by a Gas Safe engineer
  • More than one significant repair a year — the maths stops working
  • An old non-condensing boiler that's also unreliable — modern condensing boilers waste less heat, so replacement recovers some cost in running savings

Questions to ask before agreeing to a new boiler

  • What specific part has failed? (A real diagnosis names a component.)
  • What would the repair cost, even if you don't recommend it?
  • Are parts still available for my model?
  • Is the heat exchanger sound?
  • Can I see your Gas Safe ID?

An engineer who can't or won't answer these is selling, not diagnosing. Get a second opinion before signing anything — a genuine replacement case survives a second look.

Need a diagnosis rather than a sales pitch?

RenoPlumb London's Gas Safe registered engineers diagnose first and quote both options where both exist — repair cost and replacement cost — so the decision is yours with real numbers. Call 07460 824073 or see our emergency boiler repair service if you have no heating or hot water right now.

What Customers Say

“They came round to service my boiler and straight away spotted a carbon monoxide leak coming from the flue at the top of the boiler.”
Mayarun Nessa · Google review

FAQs

Is it worth repairing a 10-year-old boiler?

Usually yes, if the fault is a single component — a pump, fan, diverter valve, or PCB — and the heat exchanger is sound. A 10-year-old boiler with a full service history can run well for years more. It stops being worth it when faults start arriving in clusters or the heat exchanger itself fails, which is typically the most expensive part.

When should a boiler definitely be replaced?

When the heat exchanger has failed, when parts are no longer manufactured for the model, when it's condemned as unsafe, or when repeated faults mean you're paying for repairs more than once a year. An old non-condensing boiler that's also unreliable is a strong replacement case because a modern condensing boiler recovers some cost through efficiency.

Do plumbers push boiler replacements unnecessarily?

Some do — a replacement is a bigger invoice than a repair, and 'it's not worth fixing' is hard for a homeowner to verify on the spot. Protect yourself by asking what specific part has failed, what the repair would cost, and why replacement is better. A trustworthy engineer can answer all three. We quote the repair option whenever one genuinely exists.

Can old boilers still get spare parts?

Manufacturers typically make spares for around 10 years after a model is discontinued, and common models stay repairable well beyond that through pattern parts and reconditioned components. Availability is model-specific — we check part availability for your exact model before telling you a boiler is unrepairable.

Who can legally repair or replace a gas boiler?

In the UK, anyone working on a gas boiler must be on the Gas Safe Register — it's illegal otherwise. Always ask for the engineer's Gas Safe ID card and check the licence number covers boiler work. All RenoPlumb gas and boiler work is carried out by Gas Safe registered engineers.

How much does boiler repair cost in London?

It depends on the failed part and the model, so we diagnose first and give a free, fixed quote before any work — you'll know the repair cost and can weigh it against a replacement quote at the same time. See our pricing page for how we price jobs.

Boiler playing up? Get an honest diagnosis

Free, no-obligation quotes for most jobs — call now and we'll talk you through next steps.

Call 07460 824073