No hot water almost always comes down to one of five things: lost power, no gas supply, a faulty thermostat or heating element, a leak or pressure fault, or a system that’s simply too old or too small for the modern demands of your household. Which one it is depends on your system type, whether that’s electric, gas, solar, heat pump or continuous flow. A few of these are safe to check yourself, but the rest need a professional.
| Safety sign | What to do |
| Gas smell | Turn off the gas supply if safe, ventilate the area, and call a licensed gasfitter |
| Water pooling around the system | Turn off the water supply if safe and call a plumber |
| Switchboard keeps tripping | Stop resetting it and book an inspection |
| Water is dangerously hot | Likely a thermostat or tempering valve fault |
| Banging, hissing or electrical noises | Stop using the unit |
| An old tank leaking from the body | Usually means replacement, not repair |
Please remember that safe checks are limited to what you can see from the outside. Gas, wiring, and internal valves are jobs for a licensed professional.
Electric hot water systems, heat pumps and solar-boosted units all rely on electricity, so this is the first thing to check if you’ve got no hot water at all. A tripped circuit breaker or blown fuse is the usual cause, and some electric water heaters also have a safety cut-off with its own reset button that can trip if the unit overheats.
Many electric storage systems only reheat overnight on an off-peak tariff so a fault can go unnoticed until the next morning’s cold shower.
Safely check whether other appliances still have power, whether a breaker has tripped at the switchboard, and whether the unit itself looks switched on. Don’t open panels or touch wiring. If the circuit breaker trips again, there’s a burning smell, or the unit has power but still runs cold, that’s a faulty element or thermostat, and you will need to call a professional.
Gas storage and continuous-flow gas systems require a working gas supply, burner, and ignition. Older gas systems often rely on a continuously burning pilot light that can blow out in wind or fail due to a thermocouple issue, while continuous-flow units can refuse to ignite due to a gas, electrical, or water-pressure fault.
Check other gas appliances and look for an error code on the display. Only relight a pilot light if your manual covers it. Call a licensed gasfitter immediately if you smell gas (often a rotten egg smell), the pilot won’t stay lit, a fault code appears, the unit ignites then cuts out, or you notice soot or scorching.
The thermostat controls water temperature, and heating elements heat the water in most electric storage tanks. A faulty thermostat can leave you with water that’s too hot, too cold, or inconsistent, while a single failed element in a larger tank often means some hot water before it runs out quickly. Solar systems lean on a booster when there isn’t enough sun, and heat pumps can develop their own compressor or sensor faults.
Common signs include lukewarm water, hot water running out faster than usual, or a powered tank that won’t reheat properly. Don’t remove panels or test elements yourself. Instead, note the symptoms along with the system’s brand, model, and age, and have a professional plumber diagnose it.
Not every hot water problem starts at the heater. A pressure relief valve, a temperature-pressure relief valve, a tempering valve, or the pipework connecting them can affect water temperature, water flow, and safety. A leaking water heater tank forces the system to keep reheating; a faulty tempering valve can leave taps running cold or deliver overly hot water at random; and a partially closed valve or low water pressure can stop continuous-flow units from firing.
Look for water pooling around the unit, dripping valve pipework, or hot water that’s fine at one tap but not another. Check for visible leaks and loose connections safely, but don’t adjust a valve yourself unless a licensed professional has told you to.
A gas leak near the tank, often noticeable as a rotten egg smell, should always be treated as urgent. A leak from the tank body itself is more serious than a small drip from a relief valve, and usually means replacement.
Sometimes nothing is broken. The system is just working harder than it was built for, especially if your household has grown or everyone showers back-to-back. Sediment buildup inside an ageing tank makes this worse, and repeated repairs on older systems often cost more than a straight replacement.
Watch for hot water running out during normal use, a system around 10 years or older, multiple recent repairs, discoloured water, a leaking tank, or rising bills without another explanation.
A newer system with one isolated fault is usually worth repairing. An old, leaking or repeatedly failing unit is usually better replaced.
| Symptom | Likely cause | Safe check | When to call a plumber |
| No hot water anywhere | Power, gas or component fault | Check switchboard or gas supply | If unresolved quickly |
| Lukewarm water only | Thermostat or tempering valve | Check all taps, not just one | For diagnosis if it persists |
| Runs out fast | Undersized tank or failing element | Note household usage | If sudden or ongoing |
| Water pooling around tank | Leak, valve or tank failure | Visual inspection only | Urgently |
| Breaker keeps tripping | Electrical fault | Stop resetting it | Immediately |
Not sure what you’ve got? Take a look at the unit itself.
Regular maintenance goes a long way toward keeping older systems reliable. Flushing the water heater tank once a year through the drain valve helps clear sediment before it builds up and starts affecting heating efficiency, and this matters even more in hard water areas, where corrosive elements in the water accelerate tank corrosion.
Having the anode rod checked and replaced as needed is also one of the most cost-effective ways to protect a tank from long-term corrosion. If you notice loose connections or rust, or your system needs an emergency plumber more than once a year, it’s usually a sign that the unit is nearing the end of its working life.
Same Day Hot Water Service handles hot water repairs, replacements, installations and new system selection across major brands including Rheem, Rinnai, Dux, Bosch, Vulcan, Aquamax, Quantum, Evoheat and Stiebel Eltron, with same-day support across Sydney, Melbourne, Adelaide, Brisbane, Perth, Newcastle, Central Coast, Wollongong, Sunshine Coast, Canberra and the Gold Coast.
If your hot water isn’t working and you need help fast, call Same Day Hot Water Service on 1300 721 996 or request a quote online.
Usually a tripped circuit, a gas or pilot light problem, a faulty thermostat or heating element, or a leak, depending on your system type.
Check whether every tap is affected, look at the switchboard, confirm other gas appliances are working, and check for visible leaks or error codes.
Commonly, a faulty thermostat, a failing tempering valve, sediment build-up, or a system that’s too small for your household.
Sometimes, if your manual recommends it. But if the breaker or fault code keeps returning, call a professional plumber instead.
Repair suits a newer system with one clear fault. Replacement suits an older system, one leaking from the tank, or one that keeps failing.
A licensed plumber or gasfitter, depending on the system and the fault. Same Day Hot Water Service can diagnose, repair, replace or install across major Australian cities.