Heating On but No Hot Water
Central heating radiators work normally but the hot water taps run cold.
What Is Causing This?
- 1Faulty diverter valve stuck in heating-only position
- 2Broken mid-position valve
- 3Hot water cylinder thermostat set too low or failed
How Urgent Is This?
This should be fixed in the coming weeks. Leaving it may allow the problem to worsen and cost more to repair.
What Needs to Be Done
A heating engineer will test the diverter or mid-position valve, check the cylinder thermostat, and replace the faulty component to restore hot water.
How Much Will It Cost?
National average estimate
Labour: £565 – £1,488 | Materials: £363 – £1,238
Enter your postcode for a local price estimate
Prices are estimates based on typical UK rates. Actual costs depend on the specific issue, accessibility, and your location. All quotes from tradespeople on Tradesfolk are completely free.
Find a Heating Engineer
Enter your postcode above to find local heating engineers, or browse all heating engineers.
Find a Heating EngineerWant a More Accurate Diagnosis?
Upload a photo of the problem and our AI tool will give you a detailed diagnosis, estimated cost, and connect you with local tradespeople.
Try Snap and FixStill Not Sure? Ask a Tradesperson
Post your question and get free advice from tradespeople who deal with this every day.
Ask a QuestionHow to Prevent This
Have the diverter valve checked during annual boiler servicing. Set the cylinder thermostat to 60 degrees. Avoid switching the system on and off frequently.
Related Problems
Hot water taps run cold or lukewarm despite the boiler or immersion heater being switched on.
Both the central heating and hot water have stopped working completely, often during cold weather.
The room thermostat does not respond, displays incorrectly, or the heating does not follow the set temperature.
Other Heating Engineer Problems
Radiators that are hot at the top but cold at the bottom, reducing heat output.
Banging, gurgling, ticking, or clicking sounds from radiators, pipes, or the boiler when the heating is running.
The room thermostat does not respond, displays incorrectly, or the heating does not follow the set temperature.
Underfloor heating that has stopped producing heat or heats unevenly across the floor.