Why Is My Shower Going Cold After a Few Minutes?
If your shower starts hot but then turns cold after a few minutes, it is a common problem in UK homes and usually points to an issue with the boiler, hot water system, or plumbing. While it can feel like a problem with the shower itself, the cause is often elsewhere.
This guide explains the most common reasons this happens and when it is time to call a professional.
High demand on a combi boiler
Many homes in the UK use combi boilers, which heat water on demand rather than storing it. If another hot tap is used while you are showering, such as a kitchen tap, washing machine, or dishwasher, the boiler may struggle to supply enough hot water.
When demand exceeds what the boiler can deliver, the water temperature can drop suddenly, causing the shower to go cold.
Faulty diverter valve
The diverter valve controls whether hot water is sent to your taps or your heating system. If this valve is worn or sticking, it may redirect hot water away from the shower while it is running.
This can result in:
Hot water at the start of the shower
Sudden temperature drops
Inconsistent hot water at taps
Diverter valve issues require inspection and repair by a qualified engineer.
Low water flow or pressure
Boilers need a minimum flow rate to operate correctly. If the flow drops too low, the boiler may reduce output or shut down briefly, causing cold water to come through.
Low flow can be caused by:
Blocked filters or shower heads
Plumbing restrictions
Issues with the incoming mains supply
This is more common in older properties or flats with shared water systems.
Thermostatic shower valve problems
Thermostatic shower valves are designed to keep water temperature stable. Over time, limescale or wear can affect how well the valve mixes hot and cold water.
A faulty shower valve can cause:
Sudden temperature changes
Water turning cold mid shower
Difficulty maintaining a steady temperature
In some cases the shower valve may need cleaning, repair, or replacement.
Boiler faults or settings
If the boiler itself is struggling to maintain hot water temperature, the issue may be internal. Common causes include worn components, faulty sensors, or incorrect settings. If your boiler pressure is low, this can also affect performance. Boiler pressure should usually sit between 1 and 1.5 bar.
When to call a Gas Safe engineer
If your shower keeps going cold and basic checks do not resolve the issue, it is best to have the system checked professionally. Shower temperature problems are often a sign of a wider issue that can worsen over time if left untreated.
A Gas Safe registered engineer can identify whether the problem lies with the boiler, heating system, or plumbing and advise on the safest solution.
Local help in West London
West Gas Service regularly diagnoses hot water and shower issues across West London, providing clear advice and reliable repairs for gas, heating, and plumbing systems. If you need help, call 07866 567112, email ralphwestgas@gmail.com, or submit a form and a qualified Gas Safe engineer will be in touch.
