Work out why you have no hot water

Work through boiler pressure, settings, and pipes step by step to find why your hot water has stopped working.

NHW-01Work out the patternCheck whether you have no heating at all, or heating but no hot water. Also check if it's every tap or just one. If every tap in the house is cold and the heating is fine, the fault is likely the boiler's hot water side or the cylinder thermostat, not the whole system. If both heating and hot water are out, suspect the boiler itself, its power supply, or gas supply.

NHW-02Check the boiler display and lightsLook at the boiler's display panel or indicator lights. Most modern boilers show a fault code or a flashing light when something's wrong. Write the code down and check the manual or the manufacturer's website — this often tells you exactly what's needed, such as low pressure or an ignition fault.

NHW-03Check the boiler pressure gaugeFind the pressure gauge on the front of the boiler. It should normally sit between 1 and 1.5 bar when the heating is off and cold. If the needle is in the red zone or near zero, low pressure is likely stopping the boiler firing. Most boilers have a top-up procedure using a filling loop, described in the manual — do this only if you're confident, otherwise call an engineer.

NHW-04Check the thermostat and hot water timerCheck the room thermostat and any hot water programmer or timer are set correctly and switched on. On combi boilers, check the hot water temperature dial hasn't been turned down or off. On systems with a separate timer, make sure the current time and day are set right, as a wrong clock can mean it thinks hot water should be off.

NHW-05Check for a frozen condensate pipeIn cold weather, many boilers cut out because the condensate pipe (a plastic pipe running outside, usually to a drain) has frozen and blocked. Look outside for the pipe and check for ice inside it. If frozen, thaw it gently by pouring warm — not boiling — water over the pipe, or wrapping a covered hot water bottle around it. Then reset the boiler.

1 each · Hot water bottle or thermos of warm water

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NHW-06Reset the boilerOnce you've fixed any obvious cause (low pressure, frozen pipe, wrong settings), reset the boiler using the button on the front panel, following the on-screen instructions or manual. Wait a few minutes for it to fire up and check the display shows normal running, not a fault code.

NHW-07Check the immersion heater, if fittedIf you have a hot water cylinder with an immersion heater, try switching it on at the wall switch, usually near the airing cupboard, and give it 30-45 minutes to heat the tank. If this restores hot water, the fault is likely with the boiler's heating of the cylinder, not the immersion heater itself.

NHW-08Know when to call a Gas Safe engineerIf pressure, settings and the condensate pipe are all fine but you still have no hot water, or the boiler shows a fault code you can't resolve, stop and call a Gas Safe registered engineer. By law, only a Gas Safe registered engineer can work on a gas boiler or its gas connections. Never open the boiler casing or attempt gas-related repairs yourself.

RULES

KNOW THE RULES

Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may work on gas appliances such as boilers.

KNOW THE RULES

Before you start: What gas work can I legally do myself?

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