If your Rheem hot water system has stopped working and there’s no hot water, there’s probably a code flashing on the front panel; don’t ignore it, this code is helpful since it will tell you exactly what’s gone wrong.
In this article, we’ll break down the most common error codes across models of Rheem hot water systems, like continuous flow, heat pump, and hot water storage systems. As well as what they mean and some initial troubleshooting steps you can take safely, plus when you will need to call a plumber. If you still have it, it’s not a bad idea to check your owner’s guide or find it online, as fault codes can vary between models.
Not sure which type of Rheem water heater you have? Continuous flow units are the compact, wall-mounted boxes. Heat pumps have a fan unit on top of or beside a tank. And electric or gas storage systems are the big upright cylinders.
Rheem continuous flow (tankless) systems display a two-digit error code on the LED panel when a fault occurs. Whether you have a Rheem tankless water heater or a larger continuous flow water heater, the unit shuts itself down and won’t restart until the issue is addressed. These are the codes you’ll see most often.
This is the most common Rheem continuous flow fault code. The unit tried to light the burner and couldn’t. It comes down to one of three things: no gas flow reaching the unit, a faulty igniter, or a flame rod that isn’t detecting ignition.
LPG users should check the propane bottle level first. Sounds obvious, but it’s the fix about half the time. For natural gas, check whether other gas appliances in the house are working, as it could be a gas supply issue. Otherwise, make sure the isolation valve near the unit is fully open and that the power supply hasn’t tripped.
To reset, close your hot tap, switch the unit off at the power point, wait 30 seconds, then switch it back on and open the hot tap. If code 11 comes back a second time, stop there. The igniter, flame rod, or gas valve needs a technician to properly diagnose.
The burner lit fine, but the flame dropped out while the unit was running. You probably noticed your shower going cold mid-way through.
Wind is a common cause on externally mounted units, especially along the coast. A dirty flame rod, low gas pressure, or a partially blocked exhaust vent can also trigger it. Try the same power cycle as code 11. But if code 12 keeps coming back in calm weather, the flame rod likely needs a clean or the gas pressure needs checking. Either way, that’s a technician job. Ignoring recurring flame failure can lead to further damage over time.
The overheat limiter has kicked in. This is a safety device that shuts the system down when the overheat thermistor temp gets too high on the heat exchanger.
Scale build-up is the usual culprit, especially in hard water areas like Melbourne and Adelaide. A failed fan motor or severely low water flow can also cause it. Don’t keep resetting this one. Code 14 is there to prevent real damage and costly repairs down the line. Get an approved plumber to inspect the unit. Scale flushing or a part replacement is usually what’s needed.
The water coming out of the unit is too hot, so the system has shut down to prevent scalding. This can happen when the outlet thermistor temp reading fails, the mixing valve downstream is stuck, or there’s very low water flow through the unit.
Check that your hot taps are opening fully and that pressure seems normal. If it does, the thermistor or valve is likely the issue. Call a technician.
The combustion fan isn’t running properly. Could be a burnt-out fan motor, blocked blades, or electrical faults in the wiring. In Australia, spiders and insects love nesting inside the fan housing during warmer months, so that’s worth a look. Fan motor ventilation issues can also be caused by debris blocking the air supply pipe.
You can check for obvious debris or webbing around the fan area without pulling anything apart. But if the motor itself has failed, you’ll need a tech. And don’t try running the unit without a working fan. It can’t vent combustion gases safely.
The water flow valve inside the unit has failed. Usually a faulty servo motor, debris in the valve, or an electrical fault on the control board. Sometimes a blocked inlet filter contributes to the problem. This one needs a technician.
The main control board has flagged an internal error. Common causes are power surge damage (especially after storms), moisture getting in, or just age.
A PCB replacement is usually the fix. But here’s the thing: if your unit is over 10 years old, a new board plus labour can cost close to half the price of a new Rheem system. Worth getting quotes for both before you commit.
Code 03: EZ Link or remote controller communication fault. Needs a service call.
Code 05: Improper combustion detected. Usually dirty burners or a venting issue. Check the air supply pipe and exhaust vent are clear.
Code 10: Abnormally low rate of combustion. Gas is burning, but not efficiently.
Code 15: Very high temperature. More severe than code 14. Do not reset. Call immediately.
Code 24: Operational switch faulty. Needs professional help.
Code 29: Heat exchanger outlet temp too low. Likely a sensor fault.
Code 32: Outlet thermistor giving abnormal readings. Sensor needs replacing.
Code 71: Gas solenoid valve or gas type circuit board fault. Needs a service call.
Code 72: False flame detection. Safety-critical. Get it checked straight away.
Rheem heat pumps don’t show numbered codes like continuous flow units do. They actually use green and red LED flashing patterns on the controller to tell you what’s going on instead. Some newer units also have a remote control display that shows fault information.
Green flashing patterns of 1, 2, 3, or 4 flashes generally mean normal operation, and relate to standby, pre-heat, heating cycle, or freeze protection, respectively. A solid green light means your water is hot and everything is fine.
There are, however, some patterns that actually signal a problem, which you can check against your unit to hopefully help you diagnose the issue.
No green light, 1 red flash: Compressor error. This means the unit has fallen back to the electric backup element. Needs professional service.
No green light, 3 or 4 red flashes: Additional compressor fault variants. This means that the backup element is running, but the heat pump isn’t.
No green light, no red light: Complete system fault. No heating at all. Urgent service needed.
Newer models may also display alphanumeric codes: F10/F11 (backup element errors), F12 (over-temperature, try resetting first), and Fd (freeze protection when inlet water drops below 5°C).
The compressor and refrigerant circuit in a heat pump are specialised components. Under Australian regulations, only technicians with a refrigerant handling licence can work on them. Attempting repairs yourself risks potential harm and further damage to the system. So even if the unit is still producing warm water through the backup element, the heat pump side needs professional help.
Older Rheem electric and gas storage systems don’t have a digital display. They use a flashing LED near the thermostat or gas control valve to communicate faults through a blink pattern. Count the flashes, note the pause, then repeat. The flash count corresponds to a specific fault. Check your owner’s manual for the exact codes for your model.
For gas storage models, four flashes typically indicates a thermocouple or pilot light issue. Continuous rapid flashing may actually indicate normal operation on some models, so check your manual before assuming the worst.
If your electric storage Rheem has stopped heating with no flashing light at all, check your switchboard for a tripped breaker first. Systems on off-peak tariffs only heat at designated times, so a midday “failure” may simply be the tariff timer.
One thing worth noting on storage systems: if you see water dripping from the temperature pressure relief valve or expansion control valve, that’s not always a fault code situation. A small amount of water release during the heating cycle is normal. But if it’s a steady flow, get it checked.
Continuous flow: Switch off at the isolating switch or power point, wait 30–60 seconds, switch back on, then open a hot tap to trigger operation. This is the simplest way to cycle power on your Rheem system.
Heat pump: Turn off at the circuit breaker, wait two to three minutes, then restore power.
Gas storage: Turn the gas control knob to “Off” (this is a manual gas cut off). Wait five minutes, then turn to “Pilot” and follow the relighting instructions on the unit’s label.
A reset clears temporary codes caused by power outages, brief gas interruptions, or one-off sensor glitches. If the same code comes back after a reset, the underlying fault hasn’t been fixed. That’s when you need a professional.
If you’ve reset the system once and the same code comes back then it might be a good idea to stop resetting it. This is especially true for overheating codes (14, 15, 16), PCB faults (70), or any compressor issue on a heat pump, but it’s best to call a licensed plumber for proper fault diagnosis.
It’s worth thinking about the age of your system too, for example, continuous flow units typically last 15–20 years, storage systems sit around 10–12, with tank corrosion being the most common reason they don’t reach that upper range. Basic maintenance like flushing sediment and checking valves can help extend the life of your unit, but other maintenance tasks like inspecting the anode rod or testing the relief valve are best left to a professional. If you’re looking at a major part replacement on a system past the halfway mark, get quotes for both repair and replacement so you can make a proper comparison. Sometimes correct installation of a new system works out cheaper than patching an old one.
Same Day Hot Water Service has been handling Rheem hot water repairs across Australia for over 30 years. Your hot water and safety are our top priorities, which is why we offer affordable service with same-day availability, and we carry the full range of Rheem hot water systems if replacement turns out to be the better call.