Nobody plans a hot water replacement. It's almost always reactive — cold shower, panic search, emergency install. But hot water systems give you weeks (sometimes months) of warning before they actually fail. If you know what to look for, you can replace on your terms rather than scrambling for whatever the on-call plumber has on the truck.
Typical lifespan by system type
- Electric storage tank: 10–15 years (Illawarra coastal homes often closer to 10)
- Gas storage tank: 8–12 years
- Gas continuous flow (Rinnai Infinity, Rheem Metro): 15–20 years
- Solar hot water (rooftop collector + tank): 15–25 years on the collector, 10–15 on the tank
- Heat pump: 10–15 years (early generation), 15+ years (modern CO2 units like Reclaim)
7 signs your hot water unit is on borrowed time
- Hot water is rusty, discoloured or has a metallic taste — the tank lining or anode has gone
- Banging, popping or whistling from the tank — sediment build-up that insulates the heating element
- Showers cool off faster than they used to — failing thermostat or heat-exchanger scale
- Water pooling, weeping or drip-staining around the base — the tank itself is leaking and won't be repaired
- Pilot light or ignition won't stay lit on gas units — failing thermocouple, ignition module or gas valve
- Power bills creeping up with no usage change — failing thermostat causing the element to run constantly
- Surface rust on the outside of the body — usually well underway on the inside too
The year-5 maintenance that doubles tank life
Every storage hot water tank has a sacrificial magnesium anode that corrodes instead of the steel tank wall. By year 5–6 the anode is usually 50–80% consumed; once it's gone, the tank lining starts to corrode and you're on borrowed time. Replacing the anode at year 5 is a quick service job and routinely adds 4–6 years of tank life. Almost nobody does it because almost nobody knows about it — your original installer didn't tell you about it.
Repair vs replace
Our rough rule on-site: if the quoted repair is a significant share of a like-for-like replacement, replace. By year 10 you're throwing good money at a tank with little life left in it. Our full repair-vs-replace guide walks through the decision tree.
Choosing the next one
If you've still got a working unit and time to plan, you have real choices: stick with what's there (simplest), upgrade to gas continuous flow (no more running out), or switch to a heat pump (lowest running costs). We compare the three big brands in our Rheem vs Rinnai vs Dux guide.