Boiler help
Boiler Working but No Hot Water? A London Homeowner’s Checklist
A safe checklist for loss of hot water, including controls, pressure, fault codes and when to book a boiler engineer.
Check that the boiler has power, the controls are calling for hot water, system pressure is within the manufacturer’s range and no fault code is displayed. If heating works but hot water does not, the cause may involve a diverter valve, sensor, flow switch or cylinder controls and usually requires an engineer.
Safe checks before booking
Confirm whether the problem affects every tap and whether the central heating still works. This distinction is useful when describing the fault.
- Check the boiler display and write down any fault code.
- Confirm the thermostat, programmer and hot-water schedule are set correctly.
- Check for a local power cut or a tripped switch, without repeatedly resetting it.
- For a sealed system, read the pressure gauge and consult the manufacturer’s manual.
- If you have a hot-water cylinder, check whether the immersion heater or cylinder controls have been changed.
Heating works but taps stay cold
On a combi boiler, this pattern can point to a component that detects hot-water demand or directs heat between the radiators and taps. On a cylinder system, motorised valves, thermostats or the programmer may be involved. These are diagnostic clues, not a reason to remove the boiler cover.
Give the engineer useful information
Provide the boiler make and model, fault code, pressure reading, when the issue started and whether heating still works. A short video of the display or unusual sound can also help the booking team understand the symptoms.
Frequently asked questions
Should I reset the boiler?
One reset may be appropriate if the manufacturer’s instructions recommend it. Repeated resets can mask a continuing fault and should be avoided.
Can a plumber fix a hot-water fault?
Faults involving the boiler or gas appliance require an appropriately Gas Safe registered engineer. A general plumber may deal with non-gas pipework or tap faults.