How Does a Gas Geyser Work? (LPG Plumbing Guide for South Africa)
24 May 2026 · Plumbers On Duty
Quick answer
A gas geyser is a tankless on-demand heater. Cold water flows in, passes through a copper heat exchanger above an LPG burner, and exits hot. The burner only fires when a tap is opened, so there is no standby heat loss and no electricity needed (except a 9V battery or piezo igniter on most models).
Big advantage in SA: completely loadshedding-proof.
The 5 key components
- Inlet water valve — senses flow when you open a hot tap
- Flow sensor — triggers the burner only when water is moving
- Burner — fires LPG (or natural gas in some metros) through a controlled jet
- Heat exchanger — copper coils carry water through the flame
- Flue — vents combustion gases safely outside (mandatory)
Sizing — what flow rate do you need?
Gas geysers are rated in litres per minute:
| Geyser size | Best for |
|---|---|
| 6 L/min | 1 outlet — kitchen OR shower, not both at once |
| 12 L/min | Small home — one shower at a time |
| 16 L/min | Average 3-bedroom — shower + basin |
| 20+ L/min | Two simultaneous showers |
Running costs vs electric
A standard 9kg LPG bottle (R350–R450 in 2026) heats roughly 2,000 litres of water from cold. For a 4-person household showering daily, that is about 6 weeks per bottle — 40–60% cheaper than running an electric geyser at peak.
Installation: not DIY
Gas geyser installs in SA require:
- A LP Gas Certificate of Conformity issued by a SAQCC-registered gas installer
- Compliant pipework (copper or stainless flexible, NOT PVC)
- A vented flue to outside — never into a roof void
- Bottle siting outside the building, 1m from openings, 3m from drains, on a stable base
- Carbon-monoxide awareness — bathrooms with gas geysers need ventilation
What it costs installed
- Bathroom-only 12L unit (with bottle, regulator, COC): R6,500–R11,000
- Whole-house 16–20L unit: R10,000–R18,000
- Conversion from electric to gas: R12,000–R22,000
Common questions
Can I install one in a flat? Usually no — body corporates almost always prohibit gas bottles indoors. Check first.
Will it work without electricity? Yes — battery-ignition models work through loadshedding.
How long does it last? 8–15 years vs 5–10 years for an electric geyser.