Electric shower running cold or losing temperature (Triton & Mira)
⚠️ This needs a qualified professional
This fault involves gas or mains electrical work. Don't attempt a DIY repair — UK law requires gas work to be carried out by a Gas Safe registered engineer. Below is what to check and describe to them, not step-by-step repair instructions.
Electric showers heat water as it passes through, rather than storing hot water, so cold spots or a gradual loss of temperature are usually about flow rate or a blocked element rather than the unit failing outright.
What’s safe to check yourself
- Check the shower head and hose for limescale build-up restricting flow — a lower flow rate through a scaled-up head can actually cause the shower to run hotter or cause temperature swings, since electric showers heat based on how fast water passes through.
- Soak a limescale-clogged shower head in a proprietary descaler or diluted white vinegar (unplug/isolate the shower first if the head needs removing near any electrical parts, though most shower heads detach at the hose with no electrical involvement).
- Check your incoming cold water pressure/flow hasn’t dropped — a shared bathroom tap running at the same time, or a partially closed isolation valve, can starve the shower of the flow it needs to heat properly.
- Check the temperature/power dial hasn’t been knocked to a lower setting.
Electric showers are a fixed mains electrical appliance, typically on their own dedicated circuit. Beyond descaling the shower head and hose (which involves no electrical parts), don’t open the shower unit itself or attempt to access its heating element — this must be done by a qualified electrician, and by law any fixed electrical work of this kind in a UK bathroom falls under Part P building regulations. If the unit is tripping your electrics or you notice any burning smell, stop using it and call a qualified electrician.