Repaired where a repair is honest and replaced where it is not, and dealt with while it is still a warning rather than an emergency on a Sunday.
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Hot water systems very rarely fail without notice. They fail without notice being taken, which is a different thing, and it is why so many of these calls happen on a weekend with no hot water in the house at all.
The clearest warning is discolouration. If the hot water has a rusty tint and the cold water from the same tap is clear, the colour is coming from inside the cylinder rather than from the supply. That generally means the sacrificial anode has been used up and the steel it was protecting has begun to corrode.
There is a second one. A tank that rumbles or knocks while it heats usually has sediment sitting on the bottom of it. Neither of those is an emergency, which is precisely the problem: nothing about them forces anybody to act, so they get lived with until the day the unit is finished.
The reason it is worth acting on is timing. A system replaced when you noticed the warning is a job booked for a weekday at a price you compared. The same system replaced when it fails is a cold shower, an urgent call and whoever can get there.
That is the cylinder talking, not the mains. Book it while it is still a choice rather than an emergency.
Run the cold tap and it is clear. Run the hot and it comes out rusty, brown or with a grey cast. That combination is the tank telling you where the discolouration is coming from, and it is not the supply.
It means the inside of the cylinder is corroding. The lining and the anode are no longer keeping water away from the steel, and what you are seeing is the steel.
It is a warning rather than an emergency, and it is the most useful one a hot water system ever gives. Almost nobody acts on it, which is why most replacements happen on the day there is no hot water at all.
A low rumble, crackle or knock as the unit heats is usually sediment sitting on the bottom of the cylinder. Water trapped underneath it boils and forces its way out, which is the noise you can hear.
It is not dangerous in itself. It is a sign the tank has accumulated material and that the element or the burner is now working through a layer to heat the water.
Taken together with discoloured hot water, the two symptoms say the same thing from different directions, and a unit showing both is worth looking at before winter rather than during it.
Every storage cylinder has a sacrificial anode in it, and its entire job is to corrode so the steel does not. It works exactly as designed right up to the point where there is none of it left.
After that the tank begins spending itself, and the clock on the replacement starts. This is the mechanism behind almost every hot water failure in Sydney.
Renewing one costs a fraction of a new unit and buys years. On a tank around six or seven years old, it is the best value item anywhere on this page.
Nothing silts up with scale here the way it does in hard-water regions, so the hard-water advice you find online does not apply to a Sydney tank.
What kills cylinders here is corrosion, which is why the anode matters so much and why the warning signs are discolouration and noise rather than a gradual loss of performance.
It also means age alone is a weak guide. A tank can be sound at fifteen years or finished at eight, and the difference is almost entirely whether anybody ever looked at the anode.
A great deal of the housing here sits directly on a slab, and a tank in an internal cupboard or a garage on that slab has nowhere useful to drain if it lets go.
Which is worth knowing before it happens. A tray and a drain line under an internal unit is inexpensive to fit while somebody is already there and it is the difference between a wet floor and a wet house.
If your unit sits inside and has no tray under it, that is worth adding to any visit rather than booking on its own.
Houses of this era get extended, and a bathroom added at the back is frequently a long way from a unit installed where the original one went. The cold water standing in that run has to be pushed out first.
That is pipe length rather than a failing heater, and no work on the unit shortens it. The honest options are a recirculation line or a small unit at that end.
The exception worth checking is a wait that has got noticeably longer than it used to be. A change is a symptom, where a constant is just geometry.
A weeping fitting on top of a cylinder is a repair. Water coming from the body of the tank is not. The steel has failed and there is no patch that anybody honest will sell you.
Turn the water off at the unit, kill its power or gas, and get the swap organised. A tank that has started to weep does not improve and it does not wait.
The failure mode when one goes properly is the entire contents on the floor at once, which on a slab means it goes wherever the floor takes it.
Some sediment can be drained off through the valve at the base of the cylinder, and on a unit that has started to rumble it occasionally helps. It is a short job and worth asking about.
It is not a cure. On a tank that is discolouring the hot water, the sediment is a symptom of the corrosion rather than the problem, and draining it does not put the anode back.
So it is worth doing on a rumbling tank that is otherwise sound, and not worth doing on a tank that is telling you it has reached the end.
The advantage of acting on a warning is that you get to compare rather than accept. Here is what separates the five options once you are actually choosing.
| Type | How it works | Expected span | The catch |
|---|---|---|---|
| Electric storage | A submerged element warms a stored volume | About 8 to 12 years | Cheapest to install, dearest to run |
| Gas storage | A burner beneath keeps the volume hot | About 8 to 12 years | Needs gas connected and flue clearances met |
| Continuous flow | Heated in transit, nothing stored | About 15 to 20 years | Needs gas and a compliant wall position |
| Heat pump | Ambient warmth moved into the tank | About 10 to 15 years | Dearer to buy, needs outdoor airflow, makes some noise |
| Solar with boost | Roof collectors with an element for poor weather | About 15 to 20 years | Needs roof area with a workable orientation |
A starting point rather than a rule. Storage is judged on how much can be drawn before it empties, so the number that counts is how many people want hot water inside one hour.
| Occupants | Electric storage | Gas storage | Continuous flow |
|---|---|---|---|
| One or two | 125 to 160 L | 90 to 135 L | 16 L/min |
| Three to four | 250 to 315 L | 135 to 170 L | 20 L/min |
| Five or more | 315 to 400 L | 170 L or twin | 26 L/min |
| Two bathrooms at once | Size up a step | Size up a step | 26 L/min |
Fixed price agreed before anything starts. These are indicative 2026 ranges.
The job to book when the warning signs have started, and it comes off the work.
The single best value job on a cylinder with life left in it.
The most common electric fault, and the reason a cold tank is not automatically a dead one.
Unit, install and removal of the old one, in one figure.
Subject to gas at the property and a wall that meets the flue clearances.
Electric storage across much of the postwar housing here, gas on properties connected for it, and continuous flow anywhere a cylinder had to come off the floor. These are the makes involved.
We service and replace these systems as an independent licensed plumber. We are not an agent for, or endorsed by, any of these manufacturers.
Colour, noise, and whether the cold from the same tap is clear. Those three answers usually tell us what we are dealing with.
Every unit carries a compliance plate with a date, and we read it out, because a real age turns repair or replace into arithmetic.
Anode, element or thermostat where that genuinely solves it. Nothing gets changed over while it has life left.
We run it, check the delivered temperature, take the old unit away and leave you the paperwork.
A licensed plumber answers directly. Repairs are usually same-day and plenty of changeovers are too.
Call 1300 381 569That the discolouration is coming from the cylinder rather than from the supply, and it is the single most useful early warning a storage system gives. Clear cold and coloured hot means the tank itself is the source, which generally means the sacrificial anode has been consumed and the steel underneath it has started to go.
No, and that is exactly why it gets ignored. It is a slow signal, months ahead of anything dramatic, and it is the best chance you will get to replace a unit on a Tuesday of your choosing rather than on a Sunday when there is no hot water at all.
Frequently, yes. Noise on heating usually means sediment sitting on the bottom of the cylinder, and it is another sign worth having looked at rather than lived with.
It is a sacrificial rod inside the tank that corrodes on purpose so the steel does not. It is consumable, and on a unit you intend to keep, replacing it is the best value job in this trade. It costs a fraction of the tank it is protecting.
Soft water. Where the supply is hard, tanks fill with scale and that is what ends them. Sydney's is not like that, so the failure mode is the anode being used up, or an element burning out, and both of those are frequently repairs rather than replacements.
Replace. Water from the body of the cylinder means the steel has gone and there is no patch for that. Shut it off and ring, because the damage compounds daily.
An anode check and report is $120 to $250. An anode replaced is $300 to $600. An element or thermostat is $250 to $550. A storage replacement is $1,400 to $2,800, and a continuous flow changeover $2,000 to $3,800.
Tell us what it is doing rather than only that it is not working. Colour, noise and whether the cold runs clear are the three that matter.
Kept if it can be kept, replaced if it cannot, and ideally before it decides for you.
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