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Boiler repair or replacement: which is best for me?

Updated on
min reading
Boiler and toolbox

Boiler breakdowns can happen when you least expect it. Being left without hot water or central heating for days on end is no fun - particularly during a cold snap. We weigh up the cost of boiler repair to see if it’s worth calling out an engineer or replacing your boiler altogether.

Fortunately, there a host of companies offering boiler repair locally, no matter where you are in the UK. However, trawling the internet looking for prices and comparing quotes can be frustrating if you don’t know what to look for.

Here at Selectra, we’ve done all the legwork for you. Read on for advice on whether to repair or replace your boiler and you’ll be enjoying hot showers again in no time!

Avoid costly calloutsFollow our boiler maintenance tips to keep yours in tip-top condition.

Should I repair or replace my boiler?

In some cases, boiler repair can be a quick and easy solution, though it could be more cost-effective in the long run to replace your boiler altogether.

Older models may not meet modern safety laws and could also be a lot less energy-efficient. The cost of repair may also be significantly increased due to replacement parts no longer being available for some older types of boiler.

We take a look at some common issues to help you decide whether it would be best to repair or replace your boiler.


1. Low boiler pressure

The dreaded 'no hot water' problem when having a shower doesn’t necessarily need a boiler replacement. A loss of water pressure could be to blame, which can be easily fixed by having the pressure release valve replaced.

2. Cold radiators

Illustration of a radiator

Bleeding your radiators should be the first thing you do if they are cold or not producing sufficient heat. If this doesn’t work, you may need to arrange for a Gas Safe engineer to carry out a chemical powerflush. A powerflush will remove deposits of sludge, rust and any other contaminants from your central heating system. Sludge, in particular, can lead to both inefficiency and breakdown of your boiler if left untreated.

3. Faulty boiler part replacements available at a low cost

You’ve worked out which faulty boiler part is responsible for the problem - if the total cost of a replacement is between £100-£200, we recommend getting your boiler repaired instead of a full replacement.

Cheaper spare parts are the thermocouple, automatic air vent and boiler ignition. More expensive boiler spare parts include the pump, fan, heat exchanger and diverter valve.


1. Heavy rust or corrosion

Impurities and acidity in your water supply can corrode the seals and electrical components of your boiler. Look for signs of corrosion or brownish rust on the external casing of the boiler, pipes and inlets.

Should an engineer discover heavy rust or corrosion, it will be very expensive to repair. If this happens, it’s best to cut your losses and get a boiler replacement.

2. Water leaks from a cast-iron boiler

If you have an older boiler with a cast-iron body, a crack may be causing water to drip onto your counters. You won’t want to have it repaired as the labour costs in dismantling the entire body and repairing it will be very expensive. It’ll be much cheaper, in the long run, to cut your losses and have your boiler replaced.

3. Failing boiler combustion

This is perhaps the most important telltale sign that it’s time to get your boiler replaced. Weak combustion can have dangerous consequences, from carbon monoxide leaks to explosions.

If you’ve noticed black soot on your boiler and an engineer has confirmed poor combustion, they’re likely to suggest a boiler replacement. In this event, don’t think twice about following the advice given - get it replaced!

4. Flue not visible

If you don’t have a modern boiler, it’s likely that the flues run through the ceiling or wall voids. This means that your engineer can’t inspect them through an inspection hatch which would otherwise have been installed with modern-day boilers. If the engineer can’t determine whether it’s installed correctly or in good condition, your boiler will be marked as ‘at-risk’.

We recommend not using your boiler until this is fixed. The cost of having inspection hatches put in, moving your boiler to another location in your home or installing new flues can be very expensive. The better option would be to have your boiler replaced entirely as this also works out cheaper and easier than going through all that hassle.

How much does boiler repair cost?

Boiler repair can cost anything between £60 and £90 per hour, depending on the day and time. Some engineers will also add a separate callout charge to the final cost.

Whatever your boiler repair issue, it should be carried out by a professional, Gas Safe registered engineer. Don’t be tempted to carry out the repairs yourself, as this could be dangerous - and even deadly, due to the risks of a gas leak or carbon monoxide poisoning.

Day or Night?

If possible, it’s best to arrange for a call-out during normal working hours, from 9am to 6pm. If you request an emergency boiler repair in the middle of the night, this could bump up the call-out rate.

Boiler parts

Below you’ll find a list of the most common components in your boiler keeping it running smoothly. These boiler repair costs below include both parts and labour.

Boiler part replacement: estimated costs
Boiler part Cost What does it do?
Boiler Fan £240 The boiler fan pushes waste gases through a pipe - or flue - to the outside of your home, where they are safely released into the air.
Thermocouple for Combi Boiler £92 A thermocouple is a safety device used to reveal whether or not your furnace's pilot light is lit. The heat from a lit flame is transmitted through the thermocouple, which keeps the gas line open.
Printed Circuit Board (PCB) £280 The PCB monitors pressure, temperatures and currents. This ensures that the boiler is working in a way that won't cause damage to internal parts.
Air vent £100 The air vent is needed to release air from headers and drums while preventing them from imploding as they raise the steam level.
Water Pump £211 This pumps hot water from the boiler to the radiators and back to the boiler again.
Pressure Relief Valve £100 The PRV is a type of safety valve. It’s used to control or limit the pressure in your boiler and avoid a build-up of pressure that might otherwise cause a boiler breakdown - or even a fire.
Thermostat Control £105 Your thermostat control regulates the boiler’s temperature. If the temperature in your home starts to drop, the thermostat switches the heating on to warm it up again.
Diverter Valve £190 The diverter valve provides heating to the radiators or to your water supply as it opens and closes. It ensures you get hot water before a warm room. If you turn your heating on, and then a hot tap, it will heat up the water to the tap first.
Gas Valve £220 The gas valve controls the flow of gas to the pilot light. The boiler is ignited by the spark generator and the gas supply continues to flow until the flow sensor has reached the desired temperature.

Can’t see the boiler part you need? Check out our Guide to Boiler Servicing to see a full list of boiler replacement parts.

It’s worth keeping in mind that, depending on the model, brand and type of boiler, replacement boiler parts can vary in price. Also, Gas Safe engineers in various parts of the country may charge different prices.

How much does boiler replacement cost?

The cost of a new boiler depends on the type of boiler you have, but will generally range from £600 to £2,500 to replace boiler systems of the same type. Swapping out one type of boiler for another will cost a lot more and with labour included can bump up the final cost to around £4,000.

Boiler replacement estimated costs
Type of Boiler Model Average Replacement Cost*
Combi or System Boiler Budget £600 - £850
Mid Range £800 - £1,100
Premium £900 - £2,000
Heat Only Boiler Standard £500 - £1,500

*Prices vary according to labour costs, location and model.

Boiler insurance

Boiler repair certainly doesn’t come cheap, so if you’d rather not pay out a fortune on getting your boiler fixed, you could purchase boiler cover to keep you protected.

Boiler cover can cost as little as £5 a month and some packages will even include unlimited callouts as part of the deal.

Our verdict

White Selectra tick on a blue background

By now you’ve identified some of the potential causes of your boiler problem. You also know the approximate cost of carrying out a boiler repair or having it replaced.

Both options can be costly and older models of boilers, in particular, can cause a lot of issues. To avoid potential boiler issues in the first place, we recommend signing up for boiler cover to keep you warm and cosy at home, all day every day.

The services and products mentioned on this website may only represent a small selection of the options available to you. Selectra encourages you to carry out your own research and seek advice if necessary before making any decisions. We may receive commission from selected partner providers on sales of some products and/or services mentioned within this website. Our website is free to use, and the commission we receive does not affect our opinion or the information we provide.

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