No hot water but heating is working fine
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →One of the most frustrating heating problems is when your radiators are toasty warm but your hot water tap runs ice cold. This issue is surprisingly common in UK homes, particularly those with combination boilers or traditional heating systems with separate hot water cylinders. The good news is that the fault usually lies with one of just a few components — most commonly the diverter valve or zone valve — which control where your boiler's heat goes. Whilst the problem feels serious, the steps to diagnose it are straightforward, and many solutions are within reach of a confident homeowner. However, if the simple checks below don't solve it, you'll need to call a Gas Safe registered engineer, as these valves require specialist knowledge and tools to repair safely.
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Most likely cause & what to check
Check your programmer or timer — make sure hot water is scheduled to be on right now, not just heating.
If you have a hot water cylinder in an airing cupboard: look for the dial on the side (cylinder thermostat). It should be set to 60°C. If it's turned right down, that's your problem.
These checks are as far as a non-tradesperson should go. Call a Gas Safe engineer and tell them: "My heating works fine but I have no hot water — could be a diverter valve or zone valve fault."
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Frequently asked questions
Why is my heating working but I have no hot water?
Your boiler has components called diverter valves and zone valves that direct hot water either to your radiators or your taps. When heating works but hot water doesn't, one of these valves is usually stuck or faulty, preventing water reaching your cylinder or taps. This is a very common fault and almost always requires a Gas Safe engineer to fix.
Could a faulty immersion heater be why I have no hot water?
If you have a separate hot water cylinder with an immersion heater, a failed heater element could be the culprit — but only if your heating system isn't supplying heat to the cylinder either. Check your programmer first to ensure hot water is actually scheduled to be on, as this is the most common cause of no hot water with working radiators.
How long does it take a Gas Safe engineer to fix a diverter valve?
Replacing a faulty diverter valve typically takes 1–2 hours once the engineer is on site. The cost varies, but budget between £150–£400 depending on your boiler type and location — call a few local engineers for quotes.
Is it safe to use an immersion heater instead if my boiler can't heat water?
Yes, if your cylinder has an immersion heater, you can use it as a temporary solution whilst waiting for a Gas Safe engineer. However, immersion heaters are expensive to run, so this should only be a short-term fix until the boiler fault is properly repaired.