Electrical safety
Immerse aquarium heaters before switching on
Restore the required water level before powering the heater again. Do not plunge a hot dry heater into water; arrange a check if it overheated.
Last reviewed: 2026-09-20
Why it matters
An aquarium heater operated out of water can overheat or crack when suddenly immersed.
Wrong action
Leaving the heater powered while draining the tank.
Correct action
Restore the required water level before powering the heater again.
What to do
- Switch off the heater and follow its cooling instructions before changing water.
- Restore the required water level before powering the heater again.
- Do not plunge a hot dry heater into water; arrange a check if it overheated.
If something happens
For serious injury, unconsciousness or difficulty breathing, keep yourself safe, call 999 and follow the operator.
Sources and review
- Electrical and Mechanical Services Department — EMSD: Household Electrical Safety Handbook sections 2.3.8-2.3.20
Last reviewed: 2026-09-20
This page provides general home-safety information and does not replace medical, legal, electrical, or other professional advice.