Gas, electric, heat pump and solar. And we check where the relief drain discharges, because on clay this heavy that is a question about your slab rather than about water.
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Every hot water tank has a relief valve that releases occasionally by design, and a drain line that has to put that water somewhere.
On sandy ground nobody thinks about where. It soaks away and disappears. On the heavy clay weathered from the rock beneath this suburb, it does not soak anywhere at all. It sits.
And clay that gets wet swells, while clay that dries out shrinks. So water landing repeatedly in one fixed spot beside a slab or a footing makes that patch of ground behave differently from the ground a metre away, and ground that moves unevenly is what cracks things.
It is slow, it is easy to miss, and it is entirely avoidable. So we look at where the discharge actually goes on any hot water visit, along with the downpipes and any air conditioning condensate, because they are the same problem in larger volumes.
On heavy clay that is worth sorting even when nothing has gone wrong yet. It is a cheap fix now and a slow expensive one later.
The heavy clay weathered from the dolerite beneath this area holds water rather than dispersing it the way sand does.
So a discharge that would vanish on sandy ground simply sits, in the same spot, every time the valve releases.
Heavy clay changes volume with moisture: swelling when wet, shrinking when dry.
Ground doing one thing in one place and the opposite a metre away moves unevenly, and uneven movement is what cracks slabs, paths and paving.
Occasional release is normal. A steady drip means the valve has stopped sealing, so the water goes in constantly rather than now and then.
Small part, small job, and worth doing promptly here for reasons that have nothing to do with the bill.
Anything discharging repeatedly into clay in one place counts, and roof water is a far bigger volume than a relief valve.
The fix is normally just directing it somewhere sensible rather than letting it run out beside a wall.
Sydney's supply is soft, so limescale is rarely what ends a unit. The anode corrodes so the tank does not.
Once the rod is gone the tank becomes what corrodes. Changing it on schedule is cheap and adds years, and almost nobody does.
Into a drain, a gully or a stormwater connection. Not onto the ground beside the building, not into a garden bed against a footing, and not to a spot where it sits.
It is a small piece of pipe and a short job to redirect. It is also the single most overlooked detail on a hot water installation on clay.
If yours discharges onto soil beside the house, that is worth changing whether or not the valve is currently weeping.
Doors that stick in one season and swing free in another. Fine cracking above a window that opens and closes with the weather. A gap at a cornice that comes and goes.
That is seasonal movement, and on reactive clay a certain amount of it is normal rather than alarming. What is not normal is one corner doing it and the rest of the house not.
A localised pattern near a discharge point, a downpipe or a leaking service is worth connecting to the plumbing rather than treating as a building problem.
A relief valve puts out litres. A downpipe in a storm puts out hundreds. Anything discharging repeatedly into clay in one place counts, and roof water is by far the biggest contributor.
So a downpipe that discharges to the ground beside the house rather than into a stormwater line is doing continuously, at scale, what a weeping valve does slowly.
It is worth looking at all of them while somebody is on the property, because they are the cheapest and largest single improvement available.
There are usually two months of notice. Hot water arriving discoloured while the cold runs clear is the tank reporting corrosion from inside.
Noise on heating, a rumble or crackle, points at sediment on the base of the cylinder.
Neither requires you to do anything today. Both are a reason to get it looked at before the weather turns rather than after the tank has gone.
A fitting weeps: repair it. The shell weeps: replace the unit. That is the whole decision, and it is usually obvious once somebody looks.
There is no patch, liner, sealant or clamp that restores a corroded cylinder, and anybody proposing one has not told you the truth about what they are selling.
In the meantime turn the water off at the unit and isolate its power or gas, particularly if it sits anywhere the water would do damage.
A tank does not care how much hot water a household uses in twenty four hours. It cares how much is drawn between about half past six and half past seven.
Which is why a system that coped for a decade can start failing without anything having gone wrong with it, when a household's routine compresses.
Teenagers are the classic cause, and so is a change in who works from home. Describe the real pattern when you ask for advice.
A shower draws hot and cold together, so the head sets the rate a cylinder is drawn down. Anything installed before the WELS labelling scheme can flow well above nine litres a minute.
A pair of heads costs a fraction of a hot water system and takes minutes to fit. If it solves the problem you have saved thousands.
If it does not, you have lost very little and you know the issue is the system rather than the draw on it.
Type and size decide most changeovers. On heavy clay there is a second question worth asking, which is what the system discharges and where that goes, because water in the wrong place here is a slow structural problem rather than a wet patch.
| System | How it heats | Typical life | What it discharges |
|---|---|---|---|
| Electric storage | An element heats a tank, often overnight on a controlled load tariff | 8 to 12 years | Relief valve occasionally, and continuously once it stops sealing |
| Gas storage | A burner under a tank keeps a stored volume hot | 8 to 12 years | Same relief arrangement and the same failure mode |
| Continuous flow | Gas heats water on demand, nothing is stored | 15 to 20 years | Nothing stored, so no tank relief discharge at all |
| Heat pump | Moves heat from the air into the tank rather than making it | 10 to 15 years | Relief discharge plus condensate, which also needs somewhere to go |
| Solar with boost | Roof collectors, with an element or burner covering the gap | 15 to 20 years | Relief discharge, and more of it on a hot day |
A starting point rather than a rule. Storage size is about how much you can draw before it runs out, so what counts is how many people want hot water inside the same hour.
| People in the house | Electric storage | Gas storage | Continuous flow |
|---|---|---|---|
| 1 to 2 | 125 to 160 L | 90 to 135 L | 16 L/min |
| 3 to 4 | 250 to 315 L | 135 to 170 L | 20 L/min |
| 5 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, no wait |
Fixed price agreed before we start. These are indicative 2026 ranges. Checking where the relief drain discharges is part of any hot water visit rather than an extra.
Element, thermostat, anode or relief valve. A relief valve sits at the lower end.
Like for like in the same position, old unit removed and taken away.
Nothing stored, and no tank relief discharge to find a home for.
Before rebate. Note it produces condensate as well as relief discharge.
Where the relief drain goes, plus downpipes and condensate if we spot a problem.
Every one of these passes through our vans regularly. Whichever badge is on yours, you get its age and its actual fault before the word replacement comes up.
We service and replace these systems as an independent licensed plumber. We are not an agent for, or endorsed by, any of these manufacturers.
Two questions that between them shape the visit, including what we check without being asked.
Anode, element, thermostat and relief valve, before anybody suggests replacing a tank that may have years left.
Where the relief drain actually ends up, and whether that is a sensible place to be putting water on this ground.
Run up to temperature, checked for leaks, and the old unit taken away if it is a changeover.
Have the age of the unit ready when you ring. On anything reasonably recent this is usually a part rather than a tank.
Call 1300 381 569Somewhere it can actually go, and on this ground that is a real question rather than a formality. A temperature and pressure relief valve releases occasionally by design, and the line has to take that water somewhere. On sandy ground it soaks away and nobody thinks about it. On heavy clay it does not soak anywhere. It sits, and clay that gets wet swells. If that discharge is landing beside a slab or a footing, you are putting water into the one material you least want to.
The clay in that spot stays wetter than the clay around it, and heavy clay changes volume with moisture. Wet clay swells, dry clay shrinks, and ground that is doing one thing in one place and the opposite a metre away moves unevenly. Over time that shows up as cracking, as a path or paving that has lifted or dropped, or as doors that stop closing properly in certain seasons. It is slow and it is entirely avoidable.
More than it looks. Occasional release is normal and healthy. A steady drip means the valve is no longer sealing, and on this ground it means water going continuously into clay in one fixed spot rather than occasionally. It is a small part and a small job, and it is worth doing promptly here for reasons that have nothing to do with the water bill.
Age decides it more than the fault does. Under about eight years a failure is usually a part: an element, a thermostat, the anode, or the relief valve. Past twelve you are spending on a tank whose lining is near the end regardless. In between it depends on what has gone and what the tank looks like inside. We test rather than guess.
Not through scale, which surprises people from harder water areas. Sydney runs soft, so limescale is rarely the cause. What fails is the sacrificial anode, a rod designed to corrode instead of the tank, and once it is used up the tank starts corroding. Replacing it on schedule is cheap and adds years, and hardly anybody has it done.
Exactly the same logic, and they are usually bigger volumes. Anything that puts water into the ground repeatedly in one spot on heavy clay is worth thinking about, and the fix is normally just getting the discharge somewhere sensible rather than letting it run out beside a wall. We will point it out if we notice it, whether or not it is what you called about.
Diagnosing and repairing an element, thermostat, valve or anode is $250 to $650, with a relief valve at the lower end. Replacing electric storage in the same position is $1,400 to $2,800. Continuous flow is $1,900 to $3,500. A heat pump starts around $3,200 before rebate. Checking where the relief drain actually goes is included on any hot water visit.
Let us know how old the unit is and whether anything stays damp near it or beside a wall. On this clay that second answer is worth mentioning even if it seems unrelated.
Parts tested first, the discharge point traced, and an honest answer on repair or replacement.
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