Written by the team at OnCall Emergency Plumbers, licensed and VBA accredited plumbers with more than 15 years of emergency work across Melbourne.
The quick decision checklist
A repair usually makes sense when:
- the system is still fairly young
- a single part has failed, a thermostat, element, valve or ignition part
- the tank itself is in good condition
- the repair cost is modest next to a new unit
Replacement is usually the better call when:
- the tank is leaking, a leaking tank usually can't be repaired
- the system is more than 10–15 years old
- several parts have failed, or repair bills keep piling up
If your situation sits in the first list, a good plumber should be talking about a repair. If it sits firmly in the second, replacement is usually the better use of your money. If it's a mix, an older unit with one failed part, say, read on.
How long does a hot water system last?
Most hot water systems last somewhere between 8 and 15 years. Where yours lands in that range depends on three things:
- Maintenance. Systems that get regular servicing, including checking and replacing the sacrificial anode in storage tanks, tend to last longer. The anode is a metal rod that corrodes so the tank doesn't. Once it's gone, the tank starts to go.
- Water quality. Hard or mineral-heavy water builds up sediment in tanks and scale in heat exchangers, which makes everything work harder.
- How hard it works. A big household running a small tank hard every morning will wear it faster than a couple with the same unit.
Hot water system lifespan isn't a countdown. A well-maintained 12-year-old unit can be in better shape than a neglected 7-year-old one. Age is a strong signal, though, which is why it's worth knowing how old yours actually is.
How to find out how old your system is
Most people don't know when their hot water system was installed, especially if they bought or rent the property. Here's how to find out:
- Check the data plate. Most units have a label or plate on the side or front with the brand, model and serial number. Many also show a manufacture date. Only look if you can reach it safely, don't climb onto a roof for a solar collector or squeeze behind a hot tank.
- Decode the serial number. If there's no clear date, some manufacturers build the manufacture date into the serial number. The brand's website or customer service line can usually tell you how to read it.
- Look for paperwork. An installation invoice, a plumber's compliance certificate or property sale documents can show when the unit went in.
- Ask your plumber. If you're booking a repair anyway, we'll check the age as part of the diagnosis and factor it into our advice.
Once you know the age, you can weigh it against the fault in front of you.
Signs your hot water system is dying
Some symptoms point to a single part. Others point to a system near the end. These are the warning signs worth paying attention to:
- Temperature not holding steady. Could be a thermostat, element, tempering valve or ignition fault, often repairable.
- Leaks around the tank. If water is coming from the tank itself, especially the base, that usually means replacement. A leak from a valve or fitting is often repairable. See leaking hot water system.
- Rust-coloured water from the hot tap. Often a sign the tank is corroding inside. Not always fatal, but worth a proper check soon.
- Unusual noises. Rumbling, banging or popping often comes from sediment build-up. Sometimes it's fixable with servicing; on an older tank it can be a sign of wear.
- Slow to heat. A failing element, thermostat or burner, or, on heat pumps, slower recovery in cold weather.
- Rising energy bills. A system working harder for the same hot water may be losing efficiency.
One sign on a young system usually means one fixable fault. Several signs on an older system usually means it's wearing out.
When a leak means replacement
This is the clearest rule in hot water. A leaking tank usually can't be repaired. Once the inner lining of a storage tank has corroded through, there's no lasting fix, patching it isn't safe or reliable.
But not every leak is the tank. Water can come from:
- the relief valve or overflow pipe: a small, constant drip is often a valve near the end of its life, which is a relief valve replacement, not a new system
- a fitting or pipe connection on top of the unit
- a tempering valve or pipework nearby
That's why we always find the source first. Water on the floor looks alarming, but a dripping valve and a failed tank are very different jobs with very different costs.
If the tank itself is leaking, switch off the power or gas to the unit, turn off the cold water valve if it's safe to reach, and call us.
Cost logic: how to weigh repair against replacement
We don't publish prices, because hot water work varies too much for a number on a web page to be honest. A failed thermostat and a split tank are very different jobs. But the logic for deciding is the same every time:
- Compare the repair to the remaining life. A modest repair on a young system buys years. The same repair on a system already at the end of its expected life might buy months.
- Count the recent repairs. If this is the second or third callout in a short time, add them up. Repair bills that keep piling up are a sign the money is better spent on a new unit.
- Think about running costs. An old, inefficient system may cost more to run. When you replace, you can choose a system that suits your household's hot water use and the utilities you have, such as gas or off-peak electricity.
- Factor in timing. A planned replacement on your terms is usually easier than an emergency one on a Sunday night.
Whatever you're weighing up, we charge by the job, not by the hour, and you approve the price on site before any work starts. More on hot water repair cost.
Will a plumber push you into replacing it?
It's a fair worry. Replacement is a bigger job than a repair, and not every business is upfront about that.
Our approach is simple: we inspect first and only recommend replacement when repair isn't practical or cost-effective. If a part can be replaced and the tank is sound, we repair it. If we think replacement is the better call, we'll show you why, the leak, the corrosion, the age on the data plate, and give you the options in plain English. The decision is yours.
If you decide to replace
When it's time for a new system, a proper hot water system replacement covers four steps:
- Assessment and system selection: your water usage, household size, available utilities and long-term running costs.
- Safe removal: disconnecting the old unit and checking connections and fittings.
- Installation and testing: every hot tap, the temperature control and the safety valves.
- Final commissioning: checking pressure levels and recovery rates.
If you're thinking about switching system type, such as gas to heat pump, have a look at our guide to hot water rebates in Victoria before you buy, and compare options on our heat pump hot water page.
If you decide to repair
Most repairs are a single failed part: an element, thermostat, ignition part, thermocouple or valve. After a repair, regular hot water system servicing is the best way to stretch the life you've got left.
Repair or replace: your questions
Should I repair or replace my hot water system?
Repair if the system is fairly young, one part has failed and the tank is sound. Replace if the tank is leaking, the system is over 10–15 years old, or several parts have failed.
How long does a hot water system last?
Most last between 8 and 15 years, depending on maintenance, water quality and how hard the system works.
Can a leaking hot water tank be repaired?
Usually not. A leak from the tank itself generally means replacement, but leaks from valves and fittings often can be repaired.
Is it worth repairing a 10-year-old hot water system?
It can be, if it's a single failed part and the tank is in good condition. If the tank is leaking or several parts have failed, replacement usually makes more sense.
How do I know how old my hot water system is?
Check the data plate on the unit for a manufacture date, or ask the manufacturer to decode the serial number. Installation paperwork can also help.
Will OnCall try to sell me a new system?
No. We diagnose first and only recommend replacement when repair isn't practical or cost-effective, and we show you why.
Not sure which way to go?
Call and describe what's happening. We'll tell you whether it sounds like a repair, a replacement, or something you can check yourself first.
Call 1800 571 216: 24/7 · Book online
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