When to Replace a Hot Water System

When the hot water starts playing up, the first question is normally whether it can be fixed or whether the whole unit has had it. Sometimes it is a cheap part. Sometimes you are putting good money into a tank that is on its way out. This guide covers the age where problems tend to start, the warning signs that point to replacement rather than another repair, and the one fault that means a new unit no matter what.

If you already know you need a new system and you are weighing up types and costs, our hot water system replacement guide goes through gas, electric, heat pump and continuous flow, along with the current Victorian rebates.

How old is your hot water system?

Age is the first thing a plumber checks, because most failures line up with the unit reaching the end of its working life. As a rough guide for what is installed in Melbourne homes:

Storage tanks (gas or electric): around 8 to 12 years.
Continuous flow (instantaneous gas): 15 to 20 years.
Heat pumps: 10 to 15 years.
Solar hot water: 15 to 20 years for the panels, less for the tank and pump.

These are general figures, not hard rules. Water quality, how hard the unit has worked and whether the sacrificial anode was ever replaced all shift the number. You can usually find the install date on the compliance plate on the side of the unit. If yours is past the range above and starting to play up, replacing it is the sensible call rather than spending more on repairs.

Signs your hot water system needs replacing

You run out of hot water sooner than you used to

If a shower that used to be fine now turns cold halfway through, sediment has probably built up in the bottom of the tank and cut into how much hot water it actually holds. On an older unit this gets worse rather than better.

Rusty or discoloured water

Brown or rusty water from the hot tap, especially first thing in the morning, points to the inside of the tank corroding. Once rust is coming through, the tank is near the end. Worth checking it is only the hot side so you are not chasing a separate pipe problem.

Water pooling around the base

Damp ground or water around the bottom of the tank is the one to take seriously. A leak from a fitting or valve can be fixed. A leak from the body of the tank cannot. There is more on that below.

Banging or rumbling noises

A storage tank that bangs or rumbles as it heats is generally sediment that has hardened on the bottom. It makes the unit work harder, use more energy and wear out faster.

Water never gets properly hot, or takes ages

Lukewarm water, or water that takes far longer to heat than it once did, can be a failed element or thermostat on an electric unit, or a burner or thermocouple fault on gas. On a newer system that is a repair. On an old one it is often the last straw.

The relief valve keeps dripping

A small drip from the temperature and pressure relief valve every now and then is normal. A valve that runs constantly, or keeps dripping after it has been replaced, can point to a pressure problem or a tired tank.

Energy bills creeping up for no reason

An old or sediment-filled unit burns more energy to do the same job. If your gas or power bill has crept up and nothing else has changed, the hot water system can be part of it.

Repair or replace: how to decide

There is no single cut-off, but a few things make the call easier:

Under about 8 years with a single failed part? Often worth repairing. Elements, thermostats, valves and anodes can all be replaced.
Past its expected life and facing a big repair? A fresh unit makes more sense than putting money into one that will fail again before long.
Repair cost creeping toward half the price of a new unit? Put it toward the new one instead.
The tank itself is leaking? Replace it. See below.

A licensed plumber can tell you quickly which of these you are dealing with. Replacing a hot water unit is licensed work in Victoria, so it is not a job to take on yourself once you get past the basic checks.

A leaking tank is not a repair

This is the one that catches people out. If water is coming from the body of the storage tank, the inner cylinder has corroded through, and there is no patching that. The fix is a new unit. Water from the tank itself, rather than a pipe or valve at the top, is worth treating as urgent, because tank leaks get worse fast and can flood the area around them.

Planning the replacement

Once you are replacing rather than repairing, it is worth a moment to think about what goes back in. A like-for-like swap is the quickest. A changeover is also a natural time to look at a more efficient option, such as a heat pump, which qualifies for Victorian energy rebates. The replacement guide compares the running costs and what each type suits.

If you would rather just get it sorted, the team at Prime Plumbing & Gasfitting can take a look and sort a hot water replacement or a repair from there. If you are not yet sure whether yours needs replacing, that is a fair thing to ask before you spend anything.

Common questions

How long should a hot water system last?

A storage tank typically gives 8 to 12 years, continuous flow gas 15 to 20, and a heat pump 10 to 15. Condition and maintenance move those numbers either way.

Is it worth repairing a 10 year old hot water system?

It depends on the fault. A single part on a unit that has been reliable can be worth fixing. A major fault, or any tank leak, on a unit that age normally means it is time to replace.

My hot water is only lukewarm. Do I need a new system?

Not always. Lukewarm water is often a failed element or thermostat on electric, or a burner or thermostat fault on gas, both of which can be repaired on a newer unit. On an old system it can be a sign it is near the end.