Geyser Parts: Thermostat, Element, Valve and Timer
Knowing the main parts of your geyser helps you understand faults, talk to the repairman and keep the geyser safe for many winters.
Updated 11 November 2026
Thermostat
The thermostat switches the element (or gas burner) off when the water reaches the set temperature and on again when it cools. A dual safety thermostat, like on the Nasgas DEG Super Deluxe, adds a second cut-off in case the first one fails. A faulty thermostat can cause cold water or dangerously hot water; replace it with the same rating.
Heating element
The element is the electric heater inside the tank, usually 1500 to 4000 W. Scale from hard water builds up on it and makes it slower and weaker. An enamel-coated element, as on Midea and Super Asia MEH models, resists scale better. If the element fails, the geyser shows power but the water stays cold.
Safety valve
The pressure and temperature safety valve releases water if pressure gets too high. It is the part that stops a geyser from bursting. Never block it. A small drip while heating is normal; a constant stream means the valve or thermostat needs checking.
Magnesium anode
The anode rod corrodes instead of the tank, so it protects the tank from rust. Check it every one to two years and replace it when it is mostly eaten away. Many Canon and Super Asia models list a magnesium anode.
Geyser timer
A geyser timer switches the geyser on only at set times, for example an hour before morning baths. It is one of the simplest ways to cut the bill. Smart geysers like Midea D50-20EFG 50 Litre Electric Geyser let you set this from a phone app.
Gas geyser parts: pilot, thermocouple and gas valve
- Pilot: a small flame that lights the main burner.
- Thermocouple: sits in the pilot flame and holds the gas valve open. When it wears out, the pilot will not stay lit.
- Gas thermostat valve: the knob that sets the temperature and opens the main burner.
- Flue and conical baffle: carry fumes out and pass extra heat to the water.
These parts are on tank gas geysers and on the gas side of gas + electric geysers.
Instant geyser parts: igniter, valve and heat exchanger
- Igniter or ignition module: makes the spark, powered by batteries or an AC adapter.
- Water flow valve or sensor: tells the geyser that a tap is open.
- Gas solenoid valve: opens the gas and shuts it if the flame goes out.
- Copper heat exchanger: the coil where water picks up heat; Canon lists 1.25 to 2.4 kg copper on the IGWH range.
- Flame sensor: checks the flame is burning.
Weak batteries are the most common cause of an instant geyser that clicks but will not light. More: tankless geyser guide.
