Common Gas Geyser Problems — What Is Wrong and What to Do
Your gas geyser has stopped working. Before you start shopping for a new one, know this: most common gas geyser faults can be diagnosed and repaired, and a fair number of them come down to flat batteries or a closed valve.
We call ourselves the Gas Geyser Hospital of George because so much of the work is diagnosis rather than replacement. we see units every week that another contractor wrote off, and a good share of them are back in service the same day.
Below are the eight faults we get called out to most. Each one covers what it feels like from inside the house, what usually causes it, what you can safely check yourself, and the point where you should stop and phone someone. Gas is not a place to experiment — anything past the basic checks belongs to a registered installer.
Gas Geyser Not Igniting
You open the hot tap and nothing happens. No click, no whoosh, no flame — just cold water running while you wait for something that never arrives.
Common causes
- Flat batteries on a Dewhot or Cadac, or no power at the plug point on a Paloma or Rinnai
- Gas supply off — an empty cylinder or a valve that was closed and never reopened
- Burner clogged with dust, insects or coastal grime
- Faulty ignition module or electrode
What you can check yourself
Change the batteries first — it is the single most common cause and it costs almost nothing. Then check the cylinder valve is fully open and give the bottle a shake to feel whether there is gas in it. On an electric unit, check the plug point has power.
When to call a professional
If the batteries are fresh, there is gas, and it still will not ignite, stop there. An ignition module, electrode or gas valve fault is not a DIY job — phone 071 551 2108.
Water Goes Hot Then Cold
The shower starts perfectly, then swings cold for ten seconds, then comes back. Usually right when someone opens a tap in the kitchen.
Common causes
- Flow rate changing because another outlet has opened
- Mixer tap interference — mixing cold in drops flow through the unit below its firing threshold
- Inconsistent gas pressure, often a nearly empty cylinder or an undersized gas line
- The unit is simply too small for the demand on it
What you can check yourself
Test it with only one tap open. If the temperature holds rock steady on its own and only swings when a second outlet runs, you have a capacity or flow problem rather than a broken geyser.
When to call a professional
If it swings on a single tap, or the cylinder is full and the gas line is short, get it diagnosed. It is often gas pressure or a flow sensor rather than the burner.
Gas Geyser Cuts Out Mid-Shower
It runs beautifully for two or three minutes and then just stops. You end the shower under cold water, and by the time you go outside to look at it the unit seems fine.
Common causes
- Thermal cutout tripping because the unit is overheating
- Gas supply interruption — cylinder running low or a regulator icing up on a cold morning
- Wind interference on an outdoor unit with no cover, blowing the flame out
- Flow sensing fault, so the geyser thinks the water has stopped
What you can check yourself
Note whether it happens on windy days only — that points straight at exposure. Check how much gas is left in the cylinder, and look at whether the unit is fitted with a weather box (Dewhot and Cadac both need one).
When to call a professional
A thermal cutout tripping repeatedly is a warning, not a quirk. Anything beyond wind exposure or a low cylinder needs a professional look.
Gas Geyser Not Clicking
You know the sound it normally makes — that rapid tick-tick-tick as the sparker fires. Now there is silence when you open the hot tap.
Common causes
- Dead batteries on a battery-ignition unit (Dewhot, Cadac)
- Battery contacts corroded, which is common in coastal George air
- Ignition module fault
- Gas valve not opening, so nothing to ignite
What you can check yourself
Replace the batteries with fresh ones — not the ones out of the remote. While the cover is off, look at the contacts for green or white corrosion and clean it off gently if you see it.
When to call a professional
Fresh batteries, clean contacts, still no click? That is an ignition module or valve issue and needs a technician.
Cold Water in the Mornings
Every other time of day is fine. But the 6am shower is lukewarm at best, and by mid-morning the problem has vanished.
Common causes
- Solar system has not recovered overnight after a cold or overcast run
- Timer or controller on a hybrid setup switching the backup off too early
- Cylinder ran empty overnight while the geyser trickled
- Preheated water being fed into a unit that cannot handle it (Dewhot and Cadac cannot)
What you can check yourself
Check whether the cylinder has gas and whether anything on your solar controller is set to a schedule. If your solar was recently installed and the cold mornings started then, that is your answer.
When to call a professional
If you have solar and want it fixed properly, an inline gas geyser is the standard solution — but only a Paloma or Rinnai can take preheated water.
Pilot Light Keeps Going Out
You relight it, it burns happily, and an hour or a day later it is out again. It usually happens overnight or on a windy afternoon.
Common causes
- Wind exposure on an unprotected outdoor installation
- Thermocouple fault — it stops sensing the flame and shuts the gas off as a safety measure
- Gas pressure issue, often a tired regulator or a cylinder near empty
- Dirty pilot assembly
What you can check yourself
Look at where the unit sits. An exposed wall in Herolds Bay or Glentana with no weather box is a pilot light problem waiting to happen. Confirm you have gas in the bottle.
When to call a professional
A thermocouple is a safety device — if it is failing, the unit is not shutting down reliably. Have it replaced rather than nursed along.
Error Codes on the Display
A number flashes on the panel and the unit refuses to run. Paloma Error 11 is the one we see most, and there are brand-specific codes on the others too.
Common causes
- Error 11 on a Paloma generally means no ignition — no gas, no spark, or the burner is not lighting
- Codes relating to flame failure, overheating or flow sensing on other units
- Power or supply interruption resetting the controller
- Genuine component failure that the unit has detected itself
What you can check yourself
Write the code down before you do anything else — it is the most useful thing you can tell us on the phone. Then check the obvious supply items: gas on, cylinder not empty, power present, water flowing.
When to call a professional
Error codes point at a specific subsystem. Send the code on WhatsApp to 071 551 2108 and we will usually know what parts to bring before arriving.
Low Water Pressure From the Gas Geyser
The hot side dribbles while the cold side runs normally. Or the geyser will not fire at all because there is not enough flow to trigger it.
Common causes
- Low incoming municipal or tank pressure
- Blocked inlet filter — grit and scale collect there over the years
- Flow restrictor fitted in the line
- Partially closed stopcock or isolating valve left half-shut after other work
What you can check yourself
Compare the hot and cold flow at the same tap. If cold is strong and hot is weak, the restriction is in the geyser or its feed, not in your municipal supply. Check no valve has been left half closed.
When to call a professional
Cleaning an inlet filter and checking flow rates is quick work for a technician. If the pressure is genuinely low across the property, the Cadac 16L Ecoflow's low-flow start is the unit designed for that situation.
When to Repair vs Replace
Repair first, almost always. Ignition modules, thermocouples, flow sensors, filters and batteries are all replaceable parts, and a good unit is worth keeping running for years.
Replacement makes sense in three situations: the heat exchanger has corroded through, the control board on an uncovered Dewhot or Cadac has been destroyed by weather and the repair cost approaches the value of the unit, or it is an unbranded import with no spares available in South Africa. It also makes sense when the unit was simply always too small for the house.
we will tell you which situation you are in before quoting. Start with gas geyser repairs or fault diagnosis, and if the answer really is a new unit, the replacement page and the buying guide cover what comes next.
Need Help With Your Gas Geyser? Call 071 551 2108
Describe the symptom in your own words — no hot water, not clicking, hot then cold — or send a photo of the unit and any error code on WhatsApp. We cover George and the Garden Route, usually the same day.