No hot water? Work through this first

No hot water has different causes depending on how your home heats it. First question: do you have a combi boiler (no hot water tank — the boiler heats water as you use it) or a cylinder (a tank, usually in an airing cupboard)?

Combi boiler: check these

• The display — an error code narrows it down fast; note it before resetting.
• The pressure gauge — below about 0.5 bar the boiler locks out. Top up to around 1.2 bar via the filling loop.
• In freezing weather — a frozen condensate pipe stops everything; see our guide for the safe thaw.
• Heating works but hot water doesn't (or vice versa) — often the diverter valve inside the boiler, which is an engineer repair.

Cylinder system: check these

• The programmer — is hot water actually scheduled on? (Power cuts scramble timers more often than people expect.)
• The room stat isn't the water stat — the cylinder has its own thermostat strapped to it, usually set 60–65°C.
• If you heat water electrically, check the immersion heater's switch and its fuse or breaker at the consumer unit.
• Boiler heats radiators but not the cylinder — commonly a stuck motorised valve on the pipework, an engineer repair.

Water's hot but runs out fast?

That's a different problem: a cylinder that's undersized for the household, a failing thermostat reading high, or an immersion heating only the top of the tank. Worth a proper look rather than living with three-minute showers.