How to Lower Hot Water Temperature — Save Money, Stay Safe
Turning down hot water saves ~£70/year in the UK — but too low risks Legionella bacteria. Here is the safe operating range and how to adjust.
Step-by-step method
1. Cylinder — minimum 60°C
HSG274 requires 60°C storage to kill Legionella. Adjust cylinder thermostat clip on the outside to 60°C. Never below 55°C.
2. Combi — 50°C at tap
Combi water is on-demand — no storage — so 50°C is safe. Turn hot water dial on boiler down to 50°C.
3. TMV at outlets
For care homes and Part G compliance (new bathrooms), fit a thermostatic mixing valve at the outlet to limit to 43°C for bath, 41°C for shower.
4. Legionella flush
Once a month, run each hot tap at max for 5 minutes. Kills bacteria in low-flow pipes.
Frequently asked questions
Is 60°C really necessary in a cylinder?+
Yes — Legionella multiplies rapidly between 20–45°C. 60°C storage kills within minutes.
How much can I save turning down hot water?+
Reducing from 65°C to 60°C saves ~5% of hot-water energy — roughly £30–£70/year for an average UK home.