Gas, electric, heat pump and solar. And on a property with a pump we check where the relief valve is discharging, because a slow drip there is measured in pumps rather than in litres.
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Every hot water tank has a temperature and pressure relief valve, and it is meant to let go occasionally. A steady drip means it has stopped sealing properly.
On most properties that is wasted water and a modest repair. Annoying, cheap, easily put off for a few months without much consequence.
On a property with a wastewater pump it is a different calculation. That discharge can end up running continuously into the pump well, which means the pump starts and stops far more often than it was designed to. Pumps are rated in starts as much as in hours.
So the cost of a weeping valve here is not the water on the bill. It is the working life of the machine, and it is the sort of thing that quietly takes years off a pump while everybody assumes the drip is trivial.
There is no reason for that unless something is discharging on its own. The hot water relief valve is the first thing to check.
Occasional discharge is normal and healthy. Water expands as it heats and the valve exists to let the excess go, so a little water at the discharge point after a heating cycle is the system working.
A steady drip is different. It means the valve is no longer sealing, or the incoming pressure is high enough that it is relieving constantly.
That distinction is the whole of this page, and it matters far more on some properties than others.
Continuous discharge into a pump well means constant cycling, and pumps are rated for a number of starts rather than for continuous duty.
So a fault that would be a minor nuisance on a gravity property becomes an expensive one here, because it is quietly consuming the life of a machine.
It also costs money continuously, because every litre relieved was heated first and has to be replaced and heated again.
Running more often than it used to, or cycling at times when nobody is using water, is frequently the first sign that something upstream is discharging steadily.
That is worth listening for. On a pumped property the machine is an accidental monitoring system for the rest of the plumbing.
If it has started cycling at night when the house is asleep, something is putting water into it, and a relief valve is the most common candidate.
A relief valve responds to pressure as well as temperature, so high incoming pressure makes it operate more often and wear out sooner.
The domestic ceiling is 500 kPa static at any outlet, and a pressure limiting valve is what holds a property below it. Those wear out at around eight to twelve years and fail open.
So a relief valve that keeps failing is frequently reporting a pressure problem rather than a fault of its own, and measuring is what tells you which.
A relief drain that has been extended, buried or routed out of sight defeats the point of it. You are meant to be able to see whether it is discharging.
It happens with the best intentions, usually during landscaping, because a small pipe terminating at ground level looks untidy.
If yours goes somewhere you cannot see, that is worth changing. It is a short job and it restores the only warning the system gives you.
Sydney's supply is soft. The sacrificial anode protects the tank by corroding in its place, and once it is gone the cylinder starts spending itself.
Scale is not what ends a tank in this city, so descaling advice written for hard-water regions does not describe your unit at all.
Renewing an anode costs a fraction of a replacement and buys years, and around the six or seven year mark it is the best value item on this page.
The compliance plate carries the date. A young system with a failed component is a repair. An old one with the same fault is usually a replacement.
Elements, thermostats and relief valves are all worth replacing on a unit under about ten years old. Past a certain age the parts stop being manufactured.
Photograph the plate and send it through before anybody drives anywhere. On steep harbourside access, a second trip is a genuine cost.
Steps, terraces, a long carry from wherever a vehicle can stop, and frequently no vehicle access to the property at all.
That is a real part of the job here rather than an afterthought, and it belongs in the quote rather than in a conversation on the day.
It is also an argument for continuous flow where it fits, because a wall-mounted unit avoids carrying a cylinder up a flight of stone steps.
Because neither of them stops you having a shower. Rusty hot water with clear cold, and a rumble on heating, are both perfectly liveable symptoms.
They are also the clearest evidence you will get that the cylinder is corroding and has accumulated material on its base.
Almost every emergency replacement we do was preceded by months of one or both. Acting on them turns an emergency into an appointment.
Close the water at the unit, turn off its electricity or gas, and ring. Those three things, in that order, and then the replacement can be arranged at a sensible pace.
Water coming from the cylinder body is the end of that unit. The steel has gone and no repair returns it.
The reason for speed is not the tank, which is already finished. It is the floor, the wall and anything below it.
Type and size decide most changeovers. On a pumped property there is a second question worth asking: what the system discharges, how often, and where that goes. A unit that sheds water regularly is working somebody else's machine.
| 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. Continuously if the valve has failed |
| Gas storage | A burner under a tank keeps a stored volume hot | 8 to 12 years | Same relief arrangement, same failure mode |
| Continuous flow | Gas heats water on demand, nothing is stored | 15 to 20 years | Nothing stored, so no tank relief discharge to worry about |
| Heat pump | Moves heat from the air into the tank rather than making it | 10 to 15 years | Relief valve plus condensate, which also has to go somewhere |
| 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. On a pumped property we check the relief discharge as part of any hot water visit.
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, nothing to run out. Needs mains gas at the property.
Before rebate. The efficient option where there is no gas to the property.
Where it goes and whether it is visible. On a pumped property this is not optional.
These are the makes we repair and install. On any visit we will tell you the age of the unit and the specific fault before a replacement is discussed.
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 whole visit, including what we check that nobody asked us to.
Anode, element, thermostat and relief valve, before anyone suggests a replacement.
Where it goes and whether it is visible, because on a pumped property that is where the expensive failures hide.
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 569It matters more here than most places, and the reason is not the water. A temperature and pressure relief valve is meant to release occasionally, and a steady drip means it is no longer sealing. On a conventional property that is wasted water and a small repair. On a property with a sewage or wastewater pump, that discharge can end up running continuously into the pump well, which means the pump cycles far more often than it was ever meant to. Pumps are rated in starts as much as hours, so the cost of ignoring it is not the water, it is the machine.
Usually the pump tells you before the valve does. It runs more often than it used to, or you hear it cycling at times when nobody is using anything. That second one is the giveaway: there is no reason for a pump to run at three in the morning in a house where everyone is asleep unless something is discharging on its own. If that is happening, the relief valve is the first thing worth checking.
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 exactly this 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 does.
It can contribute, and it is worth measuring rather than replacing the valve twice. A relief valve responds to pressure as well as temperature, so a house seeing high incoming pressure will work its valve harder and shorten its life. If the same valve has been replaced more than once in a few years, the pressure is the thing to check before fitting a third.
Somewhere safe and visible, which is the point of it. A drain line that has been extended, buried or connected somewhere out of sight defeats the purpose, because nobody sees that it is running. In a house on a pump, a discharge that has been routed quietly into the wastewater system is exactly how a weeping valve goes unnoticed for a year.
Diagnosing and repairing an element, thermostat, valve or anode is $250 to $650, and a relief valve sits at the lower end of that. 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.
Let us know how old the unit is and whether the property is on a pump. If the pump has been cycling oddly, mention that too, because the two are often the same story.
Parts tested first, the relief discharge traced, and a straight answer on repair or replacement.
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