Instant Hot Water Not Working? Understanding Error Signals

You go to take a shower, and there is no hot water. You check the instant hot water unit on the wall and see a flashing light or an error code on the display. The number means nothing to you. The manual is long gone. And now you are standing in the cold, wondering what went wrong and whether you need a new system or just a simple repair.

Continuous flow hot water systems, also called instantaneous or tankless systems, are clever pieces of technology. They heat water on demand rather than storing it in a tank. But when something goes wrong, they display error codes that most homeowners cannot interpret. A flashing light or a number on the screen could mean anything from a minor issue you can fix yourself to a serious fault requiring professional repair.

This guide covers the most common error codes from the brands we see most often in Adelaide homes: Rinnai, Bosch and Rheem. We explain what these codes typically mean, what you can safely try yourself, and when it is time to call a licensed gas fitter or plumber.

How Instant Hot Water Error Codes Work

Modern continuous flow hot water systems have electronic control boards that monitor everything happening inside the unit. When something falls outside normal operating parameters, the system shuts down and displays an error code. This is a safety feature designed to prevent damage to the unit or danger to your household.

Error codes are displayed differently depending on the brand and model. Some units have digital displays that show a number like 11, 12 or 61. Others use flashing LED lights where the number of flashes indicates the error. Some show a combination of both.

The same error code can have slightly different meanings across brands and even between models from the same manufacturer. The codes below are general guides based on the most common systems we service in Adelaide. For the exact meaning for your specific unit, the model number on your system can help us, or you can look up the precise fault.

Rinnai Error Codes

Rinnai is one of the most popular instant hot water brands in Adelaide. Their units display error codes as numbers on the digital screen or through flashing lights.

Error 11: No ignition – The unit is trying to light, but the burner is not igniting. This could mean the gas supply is off, the gas bottle is empty if you are on LPG, or there is a problem with the igniter or gas valve. Check your gas supply first. If gas is available, the unit needs professional attention.

Error 12: Flame failure – The burner ignited,d but the flame went out unexpectedly. Often caused by wind blowing out the flame on outdoor units, insufficient gas pressure, or a faulty flame rod. If it happens once on a windy day, try resetting. If it keeps happening, call a technician.

Error 14: Thermal fuse activated – The unit has overheated, and the thermal safety fuse has tripped. This is a serious fault that requires professional repair. Do not try to reset or bypass this.

Error 16: Overheating – The heat exchanger temperature is too high. May be caused by scale buildup restricting water flow, a blocked filter, or low water pressure. In Adelaide, scale buildup from our hard water is a common cause. The unit needs descaling or repair.

Error 61: Fan fault – The combustion fan is not operating correctly. Could be a faulty fan motor, blocked air intake, or wiring issue. Requires professional diagnosis and repair.

Error 65: Water flow issue – Not enough water is flowing through the unit to activate it. Check that all hot taps in the house are fully open when testing. May indicate a blocked inlet filter, low mains pressure, or a faulty flow sensor.

Bosch Error Codes

Bosch continuous flow systems are common in Adelaide, particularly the Bosch Highflow and Bosch Hydro ranges. Error codes display on the unit’s screen.

Error EA: No ignition or flame failure – The system cannot ignite, or the flame is not being detected. Similar to Rinnai codes 11 and 12. Check the gas supply first. May also indicate a faulty ignition electrode, gas valve, or flame sensor.

Error C7: Fan fault – The combustion fan is not operating at the correct speed. May be caused by a faulty fan, blocked flue, or control board issue. Requires professional repair.

Error E9: Overheating protection – The unit has shut down due to excessive temperature. Often caused by scale buildup or insufficient water flow. Adelaide’s hard water frequently causes scale to accumulate in the heat exchanger, triggering this error.

Error A7: Hot water outlet sensor fault – The temperature sensor is reading incorrectly or has failed. The unit cannot regulate output temperature safely. Sensor replacement is usually required.

Error CE: Low water pressure. Water pressure is too low for the unit to operate. Check for partially closed valves, blocked filters, or issues with your mains water supply.

Hot Water System Showing an Error Code?

We repair Rinnai, Bosch, Rheem and all major brands of continuous flow hot water systems. Same-day service available across Adelaide.

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Rheem Error Codes

Rheem continuous flow units are widely installed across Adelaide. Their error codes are typically displayed through flashing LED lights or digital displays, depending on the model.

Error 11: Ignition failure – No ignition detected after multiple attempts. Check gas supply. If gas is available, the igniter, gas valve or control board may be faulty.

Error 12: Flame failure – Flame detected but then lost during operation. Wind exposure on outdoor units is a common cause. Persistent flame failure indicates gas supply issues, a dirty burner, or faulty flame detection.

Error 14: Overheat protection – The thermal fuse has tripped due to excessive heat. This safety device prevents fire risk. Professional repair required.

Error 16: Outlet temperature too high – Water leaving the unit is hotter than the safe limit. Usually caused by restricted water flow or scale buildup. Adelaide’s hard water is often responsible. The heat exchanger may need descaling.

Error 32: Outlet thermistor fault – The outlet temperature sensor is not reading correctly. The unit cannot accurately control water temperature. Sensor replacement needed.

Error 61: Fan issue – The combustion fan is not running or is not running at the correct speed. May be a motor fault, a blockage in the flue, or a wiring problem.

What You Can Safely Try Before Calling a Plumber

Some error codes can be resolved with simple checks. Before calling a plumber Adelaide for repairs, try these steps.

Check your gas supply – Make sure the gas is turned on at the meter. If you are on bottled LPG, check that the bottle is not empty and the valve is open. Ignition errors are often caused by no gas reaching the unit.

Reset the unit – Turn off the power to the hot water system at the isolating switch for 60 seconds, then turn it back on. Some temporary faults clear after a reset. If the error comes back immediately, the fault is still present.

Check the inlet filter – Most continuous flow units have a small filter where the cold water enters. Turn off the water supply, remove the filter, and clean out any debris. A blocked filter restricts flow and can cause overheating or flow errors.

Check for obvious obstructions – Make sure the flue outlet is not blocked by leaves, debris, spider webs, or anything else. A blocked flue can cause ignition and combustion problems.

Check water pressure – Turn on a cold tap and check the flow is normal. If cold water pressure is low throughout the house, the problem is with your mains supply, not the hot water unit.

If none of these steps resolves the error, or if the same error keeps returning after reset, the unit needs professional diagnosis and repair.

When to Call a Licensed Gas Fitter

Gas hot water systems must be repaired by a licensed gas fitter. This is a legal requirement in South Australia. Attempting DIY repairs on gas appliances is illegal and dangerous.

You need professional help when:

The error persists after basic troubleshooting – If checking the gas supply, resetting the unit, and cleaning the filter do not fix it, the fault is internal.

You see overheating or thermal fuse errors – These are serious faults indicating the unit reached dangerous temperatures. They require a professional diagnosis to identify why.

The unit is producing unusual smells or sounds – Burning smells, gas odours, or unusual noises, along with an error code, suggest a more serious problem.

You have no hot water and cannot resolve it. Hot water is essential. If your troubleshooting has not worked, call for same-day repair rather than going without.

The unit is old or has not been serviced – Continuous flow systems should be serviced every two years. If your unit has not been serviced and is now showing errors, it likely needs a proper service as well as the specific fault repaired.

Adelaide’s Hard Water and Hot Water System Errors

Adelaide has some of the hardest water in Australia. The minerals in our water, particularly calcium and magnesium, build up inside hot water systems over time. This is especially problematic for continuous flow units.

Scale accumulates in the heat exchanger, the narrow tubes where water is heated. As scale builds up, water flow is restricted, and the heat exchanger has to work harder to heat the water. This leads to overheating, error codes 16 and E9, and eventually premature failure of the unit.

If your unit is showing overheating errors, scale buildup is a likely cause. The heat exchanger may need professional descaling, which involves circulating a descaling solution through the system to dissolve the mineral deposits. In severe cases, the heat exchanger may need replacement.

Regular servicing helps identify scale buildup before it causes errors. We can also advise on whether a water softener or scale inhibitor might be worthwhile for your property.

Need Your Hot Water System Repaired Today?

We carry common parts for Rinnai, Bosch, Rheem and other brands. Many repairs are completed the same day, so you have hot water back by tonight.

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Frequently Asked Questions

• How do I find the error code on my instant hot water system?

Look at the front panel of the unit. Digital displays will show a number or letter code. Some units have LED lights that flash a certain number of times to indicate the error. Check the display when you first notice the problem, as some errors clear from the screen after a period. If you cannot see the code, the manual for your model will explain how error codes are displayed.

• Can I reset my hot water system to clear an error code?

Yes, you can try resetting by turning off the power at the isolating switch for 60 seconds and turning it back on. Some temporary faults will clear after a reset. However, if the underlying problem still exists, the error will return. Repeatedly resetting without fixing the actual fault can cause further damage or mask a safety issue.

• Why does my instant hot water keep turning off?

Continuous flow units shut down when they detect a fault condition. The most common reasons are insufficient gas supply, flame failure due to wind on outdoor units, overheating from scale buildup or low water flow, fan faults, or sensor problems. The error code displayed tells you what fault triggered the shutdown.

• How much does it cost to repair an instant hot water system?

Minor repairs like replacing an igniter or cleaning a blocked filter typically cost $180 to $350. More significant repairs like replacing a gas valve, fan motor or control board can cost $400 to $800, including parts. Descaling a heat exchanger usually costs $250 to $400. We provide an upfront quote after diagnosing the fault.

• Is it worth repairing an old instant hot water system?

Continuous flow hot water systems typically last 15 to 20 years with proper maintenance. If your unit is under 10 years old, repair is usually worthwhile. Over 15 years old, consider whether repair costs are better put toward a new, more efficient unit. We can advise on whether repair or replacement makes more sense for your situation.

• Why does Adelaide water cause problems for hot water systems?

Adelaide has very hard water with high mineral content. These minerals form scale deposits inside hot water systems, especially in the heat exchangers of continuous flow units. Scale restricts water flow, reduces efficiency, causes overheating errors, and shortens the lifespan of the system. Regular servicing and descaling help manage this.

• Can I repair my gas hot water system myself?

No. Gas appliance repairs must be performed by a licensed gas fitter in South Australia. This is a legal requirement for safety reasons. You can do basic checks like verifying gas supply, resetting the unit, and cleaning the inlet filter, but any internal repairs must be done by a licensed professional.

• How often should continuous flow hot water systems be serviced?

Manufacturers generally recommend servicing every two years. In Adelaide, with our hard water, annual servicing may be beneficial for systems in heavy use. Regular servicing identifies scale buildup, wear on components, and potential faults before they cause breakdowns. It also maintains efficiency and extends the life of your system.

Get Your Hot Water Back Fast

An error code on your instant hot water system does not always mean disaster. Sometimes it is a simple issue you can resolve yourself with a reset or a filter clean. Other times, it indicates a fault that needs professional repair.

Understanding what the code means helps you know whether to try basic troubleshooting or call for help straight away. Either way, most continuous flow hot water problems can be fixed the same day, so you do not have to go long without hot water.

Note down the error code and model number before calling. This helps us prepare the right parts and diagnose the problem faster when we arrive.

Wills Plumbing Adelaide repairs all brands of continuous flow hot water systems, including Rinnai, Bosch, Rheem, Dux and Thermann. Our licensed gas fitters carry common parts on every van for same-day repairs across Adelaide. Call 0484 600 095 to book a hot water repair or service.