Why does my shower have no hot water?

The most useful two minutes here are spent working out whether the fault is in the shower or in the hot water supply. They are entirely different repairs, and the test is simply running a hot tap somewhere else.

What you'll need

• Screwdriver (optional)
• Boiler manual (optional)

Step by step

1. Run a hot tap elsewhere in the house.Hot everywhere else means the fault is the shower. No hot anywhere means the boiler, cylinder or controls. This single test halves the problem.
2. If nothing is hot, check the boiler for a fault code or lockout.Check the display, the pressure gauge, and whether the pilot or ignition is working. Many faults are a reset away.
3. Check the hot water timer and thermostat.Timers get reset by power cuts and clocks change. A boost or 'on' setting confirms whether it is a scheduling problem rather than a fault.
4. If you have a hot water cylinder, check its immersion heater and thermostat.A tripped immersion or a failed thermostat is common, and both are inexpensive parts.
5. If other taps are hot, check the shower's temperature control.Thermostatic cartridges fail and often stick to cold as a safety default. Replacement cartridges are widely available and it is a manageable DIY job.
6. Check the shower's inlet filters.Most mixer showers have small mesh filters at the inlets that clog with debris and limescale. Cleaning them is easy and frequently the whole problem.
7. Check for an isolation valve turned off.Small in-line valves near the shower can be knocked or turned off during other work. A screwdriver slot turned across the pipe means closed.
8. For an electric shower, check the pull-cord switch and the circuit breaker.Electric showers have their own high-current circuit. A tripped breaker means no heating at all, and repeated tripping means a fault that needs an electrician.

Tips

• Limescale is the leading cause of shower failures in hard water areas. Descaling the head and filters annually prevents most of it.
• A shower that runs hot then cold usually indicates a flow or pressure problem rather than a heating one — often another outlet drawing water.
• Note the shower's make and model before ordering parts. Cartridges are model-specific and rarely interchangeable.

Common mistakes

• Calling an engineer before testing another tap — That test tells you whether the fault is the shower or the whole hot water system, which changes who you should call.
• Ignoring a repeatedly tripping electric shower circuit — Repeated tripping indicates a genuine electrical fault. Resetting it repeatedly is not a fix and is not safe.
• Replacing the whole shower unit first — Cartridges and filters cause most failures and cost a fraction of a new unit.

Questions people ask