Boilers: Boiler parts and spares Boiler spares

A broken or faulty boiler can be an aggravating and potentially expensive problem to fix.

You shouldn't attempt to repair a boiler yourself - you'll need an accredited boiler engineer to complete the work - but it can help to equip yourself beforehand with details of how much different boiler spares, parts and repairs usually cost.

Common boiler spares and repairs

We asked Adrian Fuller, whose company has been highly recommended on our Which? Local service, to say how much common boiler spares and faults cost to repair.

Prices shown below are the range that Adrian’s company in Surrey has charged over the past 12 months, including parts, labour and VAT. Costs vary depending on boiler type, age and model. Labour costs will also vary, depending on where you live.

Boiler parts and replacement costs
Boiler Part	Cost to replace part (including installation)	What boiler part does
Diverter/zone valves	£118 - £533	Directs flow of heated water from the boiler for heating or hot water
Printed circuit board	£210 - £434	The ‘brain’ – it makes things run together
Pump	£139 - £389	Moves heated water from the boiler, for either heating or hot water
Fan	£203 - £630	Moves air through the boiler for combustion
Gas valve	£156 - £554	Regulates gas flow to the burner
Overheat thermostat	£83 - £360	Prevents boiler from overheating
Automatic air vent	£47 - £232	Lets air out of the boiler
Pressure relief valve	£98 - £197	Safety component that ensures pressure does not become dangerous
Thermocouple (only found in older boilers)	£57 - £145	Essential component in preventing gas leaks if your pilot light goes out
Ignition	£48 - £139	Ignites the pilot/main flame

Boiler spares

The boiler spares are listed in the order that Adrian's team needed to replace them during a 12-month period ending in June 2009. Diverter/zone valves were the most frequently replaced parts and the ignition the least.

Adrian has not needed to replace an expansion vessel in the past 12 months, but this can be quite an expensive component to replace.

We asked a professional engineer for typical boiler spares and repairs costs

The expansion vessel prevents sealed heating systems from becoming over pressurised. In our 2008 research Adrian's company had quoted an average price of £324 for replacing an expansion vessel.

Getting a good deal on boiler repairs and spare parts

Choosing a qualified and reputable boiler engineer is important when getting any boiler repairs or servicing work done. Ask friends and family, or look on Which? Local for recommendations for reliable traders and ask for a breakdown of the quoted costs, including boiler spares, parts, call-out fees, labour and VAT costs.

A regular service to your boiler should help prolong the life of your boiler and its parts, but you could be better off putting money aside in a savings account or cash Isa in the event of having to pay for boiler repairs rather than an annual boiler servicing contract. Adrian's company charges £84 for a full boiler service.

Repair or replace?

Determining the so-called tipping point at which it becomes more economical to replace an old, less efficient boiler with a high efficiency A-rated boiler can be tricky given how expensive a new boiler installation can work out.

But if you're experiencing problems with your boiler and have to pay out for repairs, it could be an opportune moment to weigh up the boiler parts and repairs bill against replacing your boiler, offset by the potential energy savings you'll make by switching to a more efficient heating system.

The amount you'll save will depend on the brand, age and type of boiler, but we've got typical energy savings calculations in our boiler efficiency guide. While the boiler scrappage scheme is now closed to new applicants, several companies are continuing to offer scrappage-style discounts when you replace an old boiler.

Boilers rated and reviewed

Find out which boilers we recommend as Best Buys in our boiler review, which covers models from Ideal, Baxi, Vaillant, Worcester, Potterton and Ariston.

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