When the radiators warm up but the taps stay cold, part of the heating system is clearly working. The fault is likely to affect how hot water is produced, stored or directed rather than the whole system.
Different boiler and cylinder arrangements behave differently, so the cause cannot be confirmed from the symptom alone. These are the common areas an engineer may consider and the checks you can make without opening an appliance.
Start with the controls
Check that the boiler or hot-water controls are switched on and that any timer is set as expected. If your system stores hot water in a cylinder, make sure the hot-water programme has not been turned off accidentally. A power interruption can sometimes reset a timer.
Look for a clear fault code on the boiler display and consult the manufacturer's instructions. A reset should only be attempted if the manual specifically recommends it; repeated resetting can hide a fault that needs attention.
Possible causes with a combi boiler
A combi boiler normally heats tap water on demand. If central heating still works, the boiler may not be detecting a request for hot water, or an internal component may not be directing heat correctly. A flow sensor, diverter valve or another control component can be involved, but only proper testing can identify the cause.
Check whether the problem affects every hot tap. If one outlet is affected while others work normally, the issue may be local to that tap or shower rather than the boiler.
Possible causes with a hot-water cylinder
Homes with a cylinder have additional controls and components. A thermostat, motorised valve, immersion heater or heat source may be involved when the central heating works but stored water is not heating. The exact arrangement matters, particularly with an unvented cylinder.
Unvented hot-water cylinders operate with safety controls and stored pressure. Do not remove covers, alter valves or interfere with discharge pipework. Inspection and repair should be carried out by an engineer with the appropriate competence for the system.
When professional help is needed
Call an engineer when the controls appear correct but there is still no hot water, a fault code persists, water is leaking, or the problem keeps returning. Details such as the boiler model, displayed code and whether every tap is affected can help the initial conversation.
TREPP & CO provides boiler fault-finding and hot-water cylinder services across North London. For urgent plumbing or heating problems, the team is available for 24/7 emergency call-outs.
- Do not remove a boiler cover or attempt repairs to gas components.
- Do not interfere with an unvented cylinder's safety valves or discharge pipework.
- If water is leaking near electrical equipment, keep clear and seek urgent professional help.
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