Hot water system leaking from the bottom: repair or replace?
Water on the floor under a hot water system means one of three things, and they have wildly different price tags. One is normal, one is a cheap repair, and one is the end of the unit. Here is how to tell them apart.
First, work out where it is actually coming from
Water finds the lowest point, so where you see it puddling is rarely where it started. Dry the area completely, put a sheet of paper towel or cardboard underneath, and come back in an hour or two. Where it gets wet first is your answer.
- 1From the drain line, in bursts, during heatingThat is the temperature and pressure relief valve doing its job. A cup or so discharging while the system heats is normal operation. A constant drip is not — that is a valve or a pressure problem and it is worth sorting, because it is quietly running your water bill up.
- 2From a fitting, valve or connectionThe cold inlet, hot outlet, the relief valve itself, the tempering valve or the isolating valve. Corrosion and mineral build-up loosen these over the years. This is normally a straightforward repair and nowhere near the cost of a replacement.
- 3Weeping from the tank body itselfNot a joint, not a fitting — the steel of the tank. This is the one nobody wants. It means the tank has corroded through from the inside, and there is no repair for it. The unit needs replacing.
If it is the tank body, turn the water off
A corroded tank does not usually give much warning between weeping and failing properly. Two hundred and fifty litres arriving at once into a laundry, a cupboard or a sub-floor does far more damage than the system is worth. Shut the isolating valve on the cold inlet, or the mains at the meter if you cannot find it.
Why tanks rust through in the first place
Most storage systems are a steel tank with a vitreous enamel lining. Enamel is good but never perfect, so a sacrificial anode is fitted — a rod of a more reactive metal that corrodes preferentially, protecting the steel. It is a consumable. Once it is used up, the tank itself starts to go.
That is the whole story behind most tank failures, and it is also why a system that gets its anode checked partway through its life often outlasts one that never does. By the time you can see water at the bottom, the anode was gone years ago and the decision has already been made for you.
The repair-or-replace call
If the leak is from a fitting and the system is under about eight years old for electric, or ten for gas, repairing is generally the right call. Beyond that, or where the tank itself has failed, replacement is the better buy — and the practical test we use is whether the repair would cost more than roughly half a new system.
There is one more consideration worth raising, because it changes the sums. If you are replacing an electric storage system, a heat pump attracts both the NSW Energy Savings Scheme, published as up to $640, and federal certificates on top, both coming off the price at the point of sale. Treat “up to” literally: NSW calls it indicative and the real figure depends on the installer, the model and the job. The full rebate picture is here, and what each system type costs is here.
Coastal properties fail earlier
The casing, valves, fittings and external pipework of a hot water system corrode noticeably faster near the surf. Systems at Gerroa, Minnamurra, Werri Beach and along Jones Beach consistently sit at the short end of the expected life range. If your system is on a coastal block and is approaching its expected life, it is worth a look before it makes the decision for you.
Inland is a different picture. A system at Jamberoo, eleven kilometres up the valley, will typically see out its full expected range with reasonable maintenance.
What we do on a leak call
We identify the source properly rather than guessing from where the puddle is. If it is a fitting, we quote the repair. If the tank has gone, we say so plainly, tell you what the replacement options are including whether a heat pump makes sense for your situation, and give you a fixed price before starting.
We are not going to quote a replacement on a system that has a loose fitting, and we are not going to sell you a repair on a tank that will fail again in three months. See hot water repairs or hot water system installation.
Questions we get asked
Is a hot water system leaking from the bottom always a replacement?
No, but it often is. If water is weeping from the body of the tank itself, the tank has corroded through and there is no repair — it has to be replaced. If the water is coming from a fitting, a valve, the cold inlet or the drain line, that is usually repairable and considerably cheaper. Working out which one you have is the first job.
Can I keep using it while I wait?
If it is a slow drip from a fitting, generally yes for a short period, with a container under it. If the tank body has failed, turn the water off to the unit — a corroded tank can go from a weep to a full failure without much warning, and a 250 litre tank emptying into a laundry or under a house does real damage. If it is inside the building rather than outside, do not leave it.
Why do hot water tanks rust through?
Most storage tanks are steel with a vitreous enamel lining, protected by a sacrificial anode — a rod that corrodes instead of the tank. Once the anode is used up, the tank starts corroding. Anodes are consumable and can be replaced, which is why an anode check partway through the system's life can add years to it. Left unchecked, the tank eventually perforates and that is the end of it.
Does coastal air make it worse?
For the casing, fittings and external pipework, definitely. Salt-laden air corrodes the outer casing, valves and connections noticeably faster, which is why systems in Gerroa, Minnamurra, Werri Beach and along Jones Beach tend to sit at the short end of the expected life range. The internal tank corrosion is driven by water chemistry and anode condition rather than salt air, but a coastal system tends to fail earlier overall.
How much does a replacement cost?
Before incentives, roughly $1,200 to $3,450 for electric storage and $3,300 to $6,900 for a heat pump in published 2026 ranges. A heat pump replacing electric attracts the NSW Energy Savings Scheme discount, published as up to $640, plus federal certificates on top, and both come off that figure. NSW calls its number indicative only, since the real discount varies by installer, location, model and how complex the install is, so we work yours out and put it in the quote. The full breakdown is on our hot water cost guide.
Need it looked at?
We do same-day hot water repairs across Wollongong, Kiama, Shellharbour and down through Gerringong and Berry. Licensed plumber and gas fitter, 24/7 for emergencies.