No hot water is one of those problems that feels urgent the moment it happens. Before you call a plumber, it’s worth running through a few quick checks, as most hot water failures come down to a short list of causes you can safely rule out yourself in under ten minutes.
Start by turning on a cold tap. If cold pressure is also low or absent, the issue is your mains supply rather than the hot water system. If cold is fine but hot is absent or weak, read on.
Check This First (All System Types)
These five checks solve a surprising number of call-outs before a plumber even needs to attend.
- Check the circuit breaker. Go to your switchboard and look for a tripped hot water breaker. It may sit between on and off rather than clearly in one position. Flip it fully off, then back on. If it trips again immediately, stop and call a plumber.
- Check the gas isolation valve (gas systems). The yellow handle on the gas pipe leading to your unit should sit parallel to the pipe when open. If it’s at an angle, the gas is off.
- Check the shut-off valve on the unit. Confirm the cold water inlet valve is fully open.
- Check whether the tank is empty. If you have a storage system and several people have showered recently, you may have simply run out. Give it one to two hours to reheat before assuming a fault.
- Check for an off-peak tariff issue. Some electric systems only heat overnight on a controlled load tariff. If yours does and you’ve used all the hot water, you may need to wait until the next off-peak window.
Electric Hot Water System Not Working
Electric storage systems are the most common type in Sydney homes. When they fail, the cause is almost always one of these.
Tripped breaker or blown fuse: The most common cause of sudden failure. If the breaker keeps tripping after resetting, there is an underlying fault that needs a licensed plumber or electrician.
High-temperature cut-off switch tripped: If the water overheated, the upper thermostat has a cut-off switch that trips as a safety measure. Look for a small reset button behind the access panel. Press it firmly, then allow one to two hours to reheat. If it keeps tripping, the thermostat or element likely needs replacing.
Thermostat set too low or faulty: Storage systems should be set to 60°C under NSW regulations. If knocked lower, water may feel lukewarm rather than fully cold. If the setting looks correct but water still isn’t heating, the thermostat may be faulty.
Burnt-out heating element: Electric tanks use one or two submerged elements. When one fails, the system may produce some hot water but not enough, or none at all. Testing and replacing an element requires a licensed plumber.
Sediment build-up: Mineral deposits settle at the bottom of the tank and insulate the element from the water. A rumbling or popping noise is a common sign. Annual flushing removes sediment and extends element life.
Failed anode rod: The sacrificial anode attracts corrosion away from the tank lining. When depleted, the tank itself corrodes. Rust-coloured water from the hot tap is the clearest sign. If the tank is already badly corroded, replacement is the only option.
System is leaking: Water pooling around the base signals a leak. For what each leak type means, see our guide on what to do when your hot water system is leaking.
| Symptom | Most likely cause | Safe DIY check |
| No hot water at all | Tripped breaker, cut-off switch | Switchboard, reset button |
| Lukewarm water | Thermostat set low, one element failed | Check thermostat setting |
| Running out faster than usual | Sediment, failing element, undersized tank | Flush tank |
| Rust-coloured water | Corroded anode or tank | Inspect anode rod |
| Water around base of unit | Leak from tank or fittings | Visual check only; call a plumber |
| Loud rumbling or popping | Sediment build-up | Flush the tank |
Gas Hot Water System Not Working
Gas systems fail differently to electric ones. Start by checking whether other gas appliances (stove, oven) are working. If they’re not, there may be a supply issue in your street. Check with your provider before assuming a unit fault.
Pilot light out (older storage units): The pilot light can be blown out by wind or draft. Relighting instructions appear on the inside of the access panel. If the pilot won’t stay lit after relighting, the thermocouple is the likely culprit.
Thermocouple failure: The thermocouple keeps the gas valve open by detecting the pilot flame. When it fails, the pilot won’t hold and the burner won’t ignite. Replacement is a straightforward job for a licensed gas plumber.
Ignition failure (continuous flow): Gas continuous flow units use electronic ignition. If you hear clicking but no ignition, check the gas supply and whether the inlet filter is blocked. Note any error codes on the display before calling.
Flue blockage: A blocked exhaust flue causes the system to shut down as a safety measure. Check for debris or obstructions around the flue outlet. Do not attempt to clear a flue yourself on a gas appliance.
| Symptom | Most likely cause | Safe DIY check |
| No hot water, no ignition | Gas supply off, pilot out | Check gas valve, relight pilot |
| Pilot lights but won’t stay lit | Faulty thermocouple | Call a plumber |
| Error code on display | Varies by model | Note the code; refer to your manual |
| Clicking but no ignition | Ignition fault, gas supply issue | Check gas supply |
| System shuts off after running | Flue blockage, overheating | Check flue outlet |
| Inconsistent temperature | Low gas pressure, blocked inlet filter | Check gas supply; clean filter |
For same-day gas hot water repairs across Sydney, our gas hot water service team is available 24/7.
Rheem Hot Water Not Working
Rheem covers electric storage, gas storage, and continuous flow models. The checks above apply to all Rheem systems. A few brand-specific points:
- Rheem electric: Repeated breaker trips usually mean a failed upper heating element. Replacement requires a licensed plumber.
- Rheem gas storage: A pilot light that won’t hold after relighting means the thermocouple needs replacing. Rheem provides relighting video guides on their website.
- Rheem continuous flow: Note any error codes on the display panel before calling. They give your plumber a head start on diagnosis.
For a full Rheem breakdown with error codes and reset steps, see our Rheem hot water troubleshooting guide.
Dux Hot Water Not Working
Dux makes electric storage (Proflo range), gas storage, and continuous flow units. Common failure points are the same as above, with two Dux-specific things to know:
- Dux electric Proflo: The reset button is behind the access panel near the thermostat. It must only be reset by a licensed plumber or electrician. If it has tripped, there is a fault that needs professional assessment first.
- Lukewarm water on any Dux type: A tempering valve that has failed in the fully open position lets too much cold water mix in, making hot water feel tepid even when the system is working correctly. This is a common Dux fault worth checking if the unit appears functional but the water never gets hot enough.
For a deeper look at hot water system types and efficiency, Energy.gov.au’s hot water guide is a useful reference.
Rinnai Gas Hot Water Not Working
Rinnai Infinity continuous flow units are the most common gas hot water system in Sydney. Before calling:
- Note the error code. Common codes are 11 (ignition failure), 12 (flame failure), 16 (overheating). For a full table and reset steps, see our Rinnai troubleshooting guide.
- Confirm the gas isolation valve is open. The yellow handle should be parallel to the pipe.
- Check the flow rate. Rinnai units need a minimum flow rate to activate. Running a single tap on low may not be enough to trigger ignition.
- Clean the inlet filter. A blocked cold water inlet filter reduces flow and can cause ignition issues.
When to Call a Plumber
Under NSW law, all gas work and most electrical hot water work must be carried out by a licensed plumber or electrician. You can verify any tradie’s licence on the NSW Fair Trading licence check before they start work.
Call a plumber immediately if:
- The circuit breaker trips repeatedly after resetting
- You smell gas at any point
- The pilot light won’t stay lit after relighting
- Water is pooling around the unit
- The unit is making loud banging, rumbling, or hissing noises
- Hot water is rust-coloured or has an unusual smell
RSP’s hot water repair team is available 24/7 across Sydney for all brands and all system types.
Key Takeaways
- Start with the basics: circuit breaker, gas isolation valve, shut-off valve, and tank level before assuming a fault
- Electric systems: tripped breaker, high-temperature cut-off, failed element, or depleted anode rod are the most common causes
- Gas systems: always check gas supply first; pilot light failure and thermocouple faults are the most common causes
- Rheem: note error codes before calling; repeated breaker trips usually mean a failed heating element
- Dux: reset button on Proflo units must only be touched by a licensed plumber; a failed tempering valve causes lukewarm water across all Dux types
- Rinnai: note the error code, confirm the gas valve is open, and check flow rate and inlet filter before calling
- Call a plumber if the breaker keeps tripping, you smell gas, the unit is leaking, or the pilot light won’t hold
Rapid Service Plumbing is a licensed Sydney plumbing service available 24/7 for hot water repairs, replacements, and same-day inspections across all brands.
