8 August 2026 · 5 min read · By the JJ Pro Plumbing team
When Should You Replace Your Hot Water System?
Hot water systems rarely die politely. They fail on cold mornings, usually a few years after the first warning signs appeared. Knowing when yours is on borrowed time lets you replace it on your schedule — not its.
How long do hot water systems last?
As a general guide: electric and gas storage tanks last 8–12 years, continuous flow (instantaneous) units 15–20 years, and heat pumps around 10–15 years. Water quality, water pressure and maintenance all shift these numbers, but if your storage tank is past ten years old, it's in the risk zone.
Not sure how old yours is? Check the compliance plate or sticker on the tank — the manufacture date is usually printed there.
Signs your system is on the way out
- Water not as hot as it used to be, or running out noticeably faster
- Rusty or discoloured hot water (but clear cold water) — a sign the tank is corroding inside
- Water pooling around the base of the unit — usually the tank has corroded through
- Rumbling, banging or popping sounds — sediment build-up making the system work harder
- Needing a repair every year or two — the repairs are buying less and less time
Repair or replace?
A simple rule covers most cases: if the tank itself is leaking, replace it — there's no economical repair for a corroded tank. If the system is under about 8 years old and the fault is an element, thermostat or valve, repair usually makes sense.
In between, weigh the repair cost against the unit's age. Spending a third of a new system's price on a ten-year-old tank rarely pays off.
Choosing a replacement
Like-for-like is the simplest path, but it's worth pausing: replacement is your one cheap opportunity to change technology. Heat pump systems cost more upfront but far less to run, and government incentives can significantly close the gap. Households on gas increasingly weigh up whether this replacement is the moment to go electric.
Size matters as much as fuel. A family of four typically needs a 250–315L storage unit or a well-sized continuous flow system — undersize it and you'll be rationing showers for a decade.
Don't wait for the cold morning
The worst time to choose a hot water system is the day yours dies, wet-haired and shivering. If your system is showing its age, get ahead of it — a planned replacement costs less and lets you choose properly.