No Hot Water But Heating Works? Six Causes
Radiators warm but taps running cold — six causes we see most often, from diverter valves to failed immersion heaters.
The reverse of the fault above — radiators heating fine, but no hot water from the taps — narrows things down to a specific short list, because it confirms the boiler itself is firing.
1. Diverter valve (combis)
Stuck in the heating position this time, the mirror image of the fault above.
2. Timer/programmer settings
Worth checking before anything else; hot water schedules get knocked off after a power cut or thermostat change.
3. Cylinder thermostat or motorised valve (system boilers)
A failed thermostat or seized valve stops the cylinder calling for heat while the heating circuit carries on normally.
4. Immersion heater failure
The element or thermostat burns out, often accelerated by hard water scale in properties relying on immersion as a backup.
5. Scaled plate heat exchanger
Hot water that's lukewarm and worsens the longer the tap runs points to scale build-up in the boiler's plate exchanger.
6. Airlock in the hot supply
Sputtering, banging taps and no flow on hot only, usually after mains work or cylinder servicing — often cleared quickly by cross-connecting hot and cold at a mixer tap.
Most calls are resolved in one visit
We carry common diverter cartridges, cylinder stats and immersion elements, so most no-hot-water calls are resolved in a single visit.