Do you think your boilers diverter valve may be stuck? Here we explain what to do to resolve this common issue.
Is your boiler’s diverter valve on the blink?
Maybe you’re stuck with lukewarm water, or your taps only work when the heating’s on. Sound familiar? You’re in the right place.
In this guide, we’ll explain what a diverter valve is, the common symptoms when it goes wrong, and what you (and more importantly, a Gas Safe engineer) can do about it.
Let’s dive in!
PS we fit new combi boilers with gas installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.
What is a Boiler Diverter Valve?
The diverter valve is basically the traffic controller of a combi boiler. It decides whether the hot water produced goes to:
Your radiators (central heating), or
Your taps and showers (domestic hot water).
It constantly switches between the two depending on demand.
👉 Important: Diverter valves are only found in combi boilers – system and heat-only boilers use a different setup.
Signs that the diverter valve is faulty
Here are some of the major signs that your boiler’s diverter valve may be faulty:
[1] Lukewarm taps/shower
This would suggest that your diverter valve is likely stuck in a position such that it only lets an amount of hot water reach your radiators, while the supply to your taps/shower is being limited.
[2] Your hot taps are working fine but your radiators won’t heat up
In this case, the diverter valve could be stuck in a position where it lets hot water reach your hot taps/shower but not your household’s radiators.
[3] The hot water taps do not work unless your central heating is turned on
Lastly, this problem may not even be noticeable until the warmer parts of the year.
After all, if you’re using your central heating quite a bit through the winter then a lack of hot water to your hot taps may not be evident until you start using your heating less and less.
Ultimately, if you find that you can only get hot water from your hot water taps when the heating is on, this would also point to a stuck diverter valve.
⚠️ Note: these are strong clues, but not 100% proof. Other boiler faults can mimic diverter valve problems.
Fixing a Stuck Diverter Valve
Unfortunately, there’s no way you can verify that a diverter valve is stuck yourself.
However, if you suspect that your boiler’s diverter valve is stuck, you must hire a Gas Safe Register engineer to take a look at it.
Gas and sealed systems = Gas Safe work only
Attempting to dismantle or unstick a valve yourself = dangerous and illegal
A faulty repair could cause leaks, gas issues, or in worst cases, an explosion
What an engineer will do:
Run tests to confirm if the diverter valve is at fault.
If it’s just stuck or gummed up, they may remove and clean it with the correct chemical solution.
If cleaning isn’t enough, the valve will need replacing.
If your boiler is under warranty and the issue is due to a manufacturing fault, you might get a free replacement.
Cost of Fixing a Stuck Diverter Valve
Here’s what you can expect to pay:
Clean & refit a stuck diverter valve – £40 to £130
Replace diverter valve – £60 to £200 (part + labour)
Replace whole boiler – £800 to £2,800*
*If your boiler is old or keeps breaking down, replacing the diverter valve may not be worth it. At that point, a new boiler could be more cost-effective long term.
Boiler Replacement on Finance
If you do need a new boiler, the upfront cost doesn’t have to sting:
Buy now, pay later – spread the cost over 12–24 months (interest-free options available)
Loans or credit card – another route, but only if repayments are comfortable
Fixed prices – so no nasty surprises down the line
Get a Quote for a New Boiler Today
If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:
Gas Safe installation within 24 hours.
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Price match guarantee: We will match any like-for-like cheaper quote.
Flexible payment options, including interest-free finance.
Up to 12-year guarantee on selected boilers.
Fixed price guarantee: No hidden costs.
Save your quote and decide later.
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