How to Fix a Faulty Diverter Valve

Last updated: November 15, 2023

Boiler breakdowns unfortunately always seem to occur when you could do without the stress, inconvenience and the additional cost.

Whilst some faults can be due to specific causes such as colder weather or power surges, faults with the diverter valve are more common with the older types of combination boilers.

In this post we will cover what a diverter valve is, the warning signs that a diverter valve could be developing a fault and the average costs involved should you need to replace the part, including the considerations that may result in a homeowner opting to replace the entire boiler rather than simply the faulty part.

What is a Boiler’s Diverter Valve?

A diverter valve is an internal boiler component that opens and closes to allow the heat generated by the boiler to warm either the hot water or the water within the heating system, or both.

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The part directs the flow of water between either the heating or hot water
and is therefore unique to combi-boilers.

Due to the moving element of the part, there are the additional risks of it getting stuck in one position, causing a restriction to either service the boiler should be undertaking.

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Faulty Diverter Valve – Signs you have one:

When a fault develops with a boiler’s diverter value it results in a number of symptoms, such as:

Luke-warm hot water (both taps and showers)

Luke-warm water from taps and showers, despite the boiler system running, is the most common symptom of a faulty diverter valve, as the part is designed to prioritise hot water however when there is a fault or a blockage, cold water mixes into the hot water and therefore the temperature is never satisfactory.

Hot water is only gained when the heating is left on

Having no hot water without the heating running is often observed in summer when the heating isn’t required, however warm water is still needed to wash.

The requirement to run the heating in order to obtain hot water is another common sign that the diverter valve has developed a fault.

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Hot water but no central heating

Another frequent symptom of a faulty diverter valve is when the valve may become stuck only on the hot water side resulting in
no heating.

If your household is experiencing any of these unhappy boiler symptoms, the likely cause is a faulty diverter valve and therefore this will require a call out from a Gas Safe registered heating engineer.

A professional will be required to safely open up the boiler unit itself and undertake tests in order to confirm the diagnosis.

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Unfortunately, some of the symptoms mentioned above can also be present within other faults and therefore an expert is required to be certain that the diverter valve is at fault, and provide quotes for any replacement parts and labour required to get the boiler back up and running again.

What are the Average Costs of Replacing a Diverter Valve?

A homeowner or landlord can expect to pay between £250 to £350 for a replacement diverter valve including the labour to fit the part, depending on the type of boiler, the location of the property and the company size quoting for the job.

If the boiler is fairly new, the parts may be covered under the original manufacturer’s warranty obtained when purchasing the boiler, however if not, it would be worth taking time to consider all of the options.

As the likely price is obviously quite a hefty bill, especially if the rest of the boiler is also ageing and other parts are suffering from wear and tear, it may be more cost-effective to purchase a whole new boiler instead.

Often boilers have a life span of between 8 and 10 years, and therefore if the boiler in question with the faulty valve is reaching the top end of this time frame, trading in for a new model with the benefits of increased fuel economy, modern technology and a new product warranty, which in turn provides peace of mind from future breakdowns.

That saying, replacing a boiler is not a cheap undertaking, with an average new boiler installation costing anywhere between £1,500 and £3,000, depending on the type of system required and the chosen boiler brand and model.

Thankfully there are a few ways of either saving money on the installation or spreading the cost as follows:

  • Save money on a new installation by using an online boiler retailer to purchase a new boiler, who can pass on the bulk buying discounts due to keeping their company overheads low
  • Spread the cost of any new boiler installation by using financing options available via multiple retailers

Got a common boiler problem? Check out our quick fix guide on boiler lockout, boiler ignition faults, boiler PCB faults, faulty diverter valves and boiler timer issues.

Faulty Diverter Valve Summary

In this post, we found out more about diverter valves including what the component is and the role it undertakes within a combination boiler.

We also discussed the frequent symptoms that can indicate that there is a problem with the internal diverter valve, as well as the importance that a Gas-Safe registered heating engineer is called out to safely investigate and to confirm the diagnosis.

The age of the boiler that has developed a fault with the diverter valve will play a part in the next steps, either to invest in replacing the part or by opting to replace the entire boiler.

Should the latter option be selected, a homeowner or landlord should obtain a number of quotes for a new boiler from reputable companies in order to compare them.

Further research into the desired boiler makes and models, as well as the latest technology available on the market such as smart thermometers and zoning can also be undertaken to find the most modern, yet suitable options for the household that should last for the next 8 to 10 years.

What size boiler is right for your home? If you are thinking about a combi boiler, it is largely determined by the number of radiators in your home.

Check out our complete guide to new boiler installation here if you are wondering about the best type of boiler for your home. 

How much may a new boiler cost? Are you considering converting from a conventional to a combi boiler? Use our boiler installation cost calculator to get an estimation.

If you require any assistance with a faulty boiler or researching purchasing a new boiler, please feel free to get in touch with our friendly team who can assist with answering your questions and providing a free, no-obligation quote.

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