Gas geyser thermostat: the right setting, faults and repair

What the thermostat does

It controls gas to the pilot and main burner. A temperature sensor in the tank tells it when water has cooled, and it opens gas to the main burner, which the pilot lights. It also contains the safety valve held open by the thermocouple.

Recommended settings

• Winter: a medium-high setting, enough for baths without scalding. Very hot settings waste gas and stress the tank.
• Summer: low, or off when not needed.
• Homes with children or elderly people: keep it moderate and test the tap temperature.
• With a timer: you can use a slightly higher setting for short heating periods, since the tank is not kept hot all day.

Signs of a faulty thermostat

• Water becomes extremely hot, or the relief valve releases water or steam.
• Main burner never fires even when the water is cold and the pilot is lit.
• The knob is stiff, broken or does not stay in position.
• Gas smell near the control: stop and call a technician.

Repair or replace?

Thermostats are sealed gas components; repairs inside them should only be done by a qualified technician, and a damaged one is usually replaced as a unit. Make sure the replacement matches your geyser’s gas type and connections.

Thermostats and auto ignition

Autopilot works with the geyser’s own unitrol-type thermostat. A healthy thermostat is needed: Autopilot lights the burner, and you still set WARM, HOT or VERY HOT on the thermostat, which controls the water temperature as before.