When a heat battery underperforms, the cause may be charging, controls, water flow, another heat source or the store itself. Start with observations and the manual, not internal adjustments.
Safe first checks
Confirm the displayed fault, time, charge state and scheduled window. Check whether the wider property has power and water, and whether another household member changed a control. Do not remove electrical covers or operate pressure-safety devices unless the manual tells you to.
Not enough hot water
Record the previous charge, any boost, shower and bath use, incoming conditions and whether flow is normal. A depleted store, missed schedule or unusually high demand can look similar.
Higher bills
Look for peak-time boosts, a tariff change, altered schedule, increased demand or another appliance. Compare half-hourly imports with a known normal week.
Faults that need prompt support
Follow the manual for leaks, burning smells, repeated electrical trips, pressure discharge, overheating or persistent error codes. Isolate only through the documented user controls and contact the responsible installer or emergency service as appropriate.
Build a useful support message
Include model, serial number, installation date, exact code, when it began, recent changes and photographs of the display and visible pipework. Avoid resetting repeatedly before recording the fault.
After repair
Ask what failed, what was changed and whether settings, warranty or service dates changed. Add the report to the property file.
Your next step
Create a one-page system record now, while everything works: support contacts, isolator locations, normal schedule and a photograph of the normal display.
Sources
Primary and independent references checked by our editorial team.
- Electrical safety: Approved Document P — GOV.UK Checked 10 Nov 2026
- Sanitation, hot water safety and water efficiency: Approved Document G — GOV.UK Checked 10 Nov 2026