No hot water but heating works? The likely culprits
If your radiators are warm but the taps run cold, here is what is usually to blame and how to get it sorted fast.
Radiators toasty but the shower running cold? It is a frustrating one, but the good news is the cause is usually specific and fixable. Here is what is likely going on.
If you have a combi boiler
A combi heats water on demand for both your heating and your taps. If the heating works but hot water does not, the prime suspect is a stuck diverter valve. This little valve is meant to switch the flow of hot water between your radiators and your taps. When it sticks toward the heating side, your radiators stay warm and your taps run cold. It is a common fault and a straightforward fix for a Gas Safe registered engineer.
Not sure whether you have a combi? Our guide on combi vs system vs regular boilers explains the difference in plain English.
If you have a system or regular boiler (with a cylinder)
Here the hot water is stored in a cylinder, so the culprits are different:
- A faulty cylinder thermostat not calling for heat
- A stuck motorised valve not letting hot water reach the cylinder
- A failed immersion heater (if you rely on one)
- Controls set wrong, worth a quick check first
What to check first
Before you call anyone, check the obvious: is the hot water programmed to be on, is the thermostat turned up, and has the boiler thrown a fault code? A quick reset sometimes clears a glitch. Manufacturer sites like Worcester Bosch list what each fault code means for your model.
When to call
If the basics check out and you still have no hot water, it is an engineer job. Whether you are with a big name like British Gas or looking for a faster local option, Norvera matches you with a vetted Gas Safe engineer near you. Tell us what is happening and we will get someone to you.
Frequently asked questions
Why do I have heating but no hot water?+
On a combi boiler this usually points to a stuck diverter valve, which sends hot water to your radiators but not your taps. On a system with a cylinder, it can be a faulty thermostat, motorised valve or immersion heater.
Can I fix no hot water myself?+
You can check your thermostat and controls and reset the boiler, but anything internal is a Gas Safe engineer job. A stuck diverter valve, for example, needs a professional.
Is no hot water an emergency?+
It is not dangerous like a gas leak, but it is disruptive. We treat it as urgent and aim for same-day help where possible.
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