Quick answer
A gas geyser pilot that will not stay lit is usually a failing thermocouple, a dirty pilot orifice, low gas supply, or wind back-draft down the flue. The thermocouple is the most common: it senses the pilot flame and shuts the gas valve when it cools, so as it ages it starts shutting the gas off while the pilot is still burning. Gas work needs a registered installer and a Gas COC.
Common causes
- Faulty thermocouple no longer holding the gas valve open
- Dirty or partly blocked pilot orifice giving a weak, lifting flame
- Low gas pressure, an empty bottle, or a regulator at end of life
- Downdraft through the flue blowing the pilot out, worse on windy days
- Flue partly blocked by a bird's nest or debris
- Unit installed in a space with inadequate ventilation for combustion air
What you can do now
- 1Check the gas bottle level and that the regulator is seated correctly
- 2Note whether it goes out mainly on windy days, which points to the flue rather than the unit
- 3Inspect the flue terminal from outside for nests or obstruction
- 4Look at the pilot flame colour — it should be crisp blue, not lazy yellow
- 5Do not attempt to clean the orifice or adjust the gas valve yourself
When to call a professional
Use a gas-qualified plumber for any gas geyser work — it requires a Gas Certificate of Compliance and is not a general plumbing job. Call immediately, not on schedule, if you can smell gas at any point: shut the bottle off at the valve, ventilate the space, and do not operate switches. A registered installer will test the thermocouple, clean the pilot assembly, verify flue draught and re-certify the installation.
Typical cost in Johannesburg
Service + thermocouple R750–R1,400
Indicative ranges only. We provide written, itemised quotes before any work.
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