No hot water? What to check before you call

Losing hot water has a handful of common causes, and a couple are safe to check yourself. What to check depends on whether you have a combi boiler or a hot-water cylinder.

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1. Is the heating working too?

If both heating and hot water are out, the boiler has likely locked out or lost power — check the fuse spur, the pressure gauge (around 1–1.5 bar when cold) and any fault code on the display. If heating works but hot water doesn't, the fault is usually the diverter valve (combi) or the cylinder controls.

2. Combi boiler checks

Note any fault code and try one reset — no more. In freezing weather, a frozen condensate pipe is a common cause; warm (not boiling) water over the outside pipe can thaw it.

3. Cylinder system checks

Check the programmer is calling for hot water and the cylinder thermostat hasn't been knocked down. If the cylinder is warm but taps run cold, the motorised valve or an airlock may be the cause — both need an engineer.

When to call

Repeated lockouts, leaks, banging noises or a boiler that won't reset need a Gas Safe Registered engineer. If you smell gas, leave the property and call the National Gas Emergency line on 0800 111 999 first.

Questions

How much does a no-hot-water repair cost?

Boiler repair diagnostics start from £95 fixed; we quote the repair itself before any work begins.

Is no hot water an emergency?

For most homes it's urgent but not dangerous — we treat it as a priority call-out. If you smell gas or see scorch marks on the boiler, treat it as an emergency and call the gas emergency line first.

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More fault guides

Smell gas? Leave the property and call the National Gas Emergency line on 0800 111 999 first.

Illustrative heating engineer inspecting a domestic boiler and copper pipework — Illustrative image, not a completed customer project.