Why is my hot water system leaking from the top?

Usually one of three things: the relief valve releasing more water than it should, a corroded pipe connection where it screws into the tank, or the cylinder itself rusting through near the top. The first two are often repairable. The third means the tank needs replacing, and it's the most likely cause on a tank over 10 years old.

Can a leaking hot water tank be repaired?

It depends on where the water is coming from. A faulty relief valve or a leaking connection can usually be replaced. A cylinder that has corroded through can't be patched safely, because it's holding hot water under mains pressure. At that point replacement is the only real option.

What should I do if my hot water system is spraying water?

Turn off the cold water isolation valve at the base of the tank, which stops more water getting in. For an electric tank, also switch off the hot water circuit at the switchboard so the element isn't heating an emptying tank. Then move anything valuable away from the water and call a licensed plumber.

How often should the relief valve on a hot water system be checked?

Rheem's own label on this unit says to ease the relief valve lever at least once every six months, and to check or replace the valve at intervals of no more than five years. Easing it takes a few seconds, and it keeps the valve from seizing so it can still release pressure when it needs to.

Who pays to replace a hot water system in a NSW strata apartment?

Under the NSW common property memorandum, a hot water system inside a lot that serves only that lot is generally the owner's responsibility. One that serves several lots, or sits outside any lot, is common property. Your building's by-laws can change this, so check them first.

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Case study · 6 min read

Hot water leaking from top, Darling Point

A 2013 Rheem electric tank was spraying water from the top in Darling Point. At nearly 13 years old, a leaking tank is a replacement, not a repair.

Adam Norton · 29 September 2026

Greg from Norton Plumbing kneeling at a leaking Rheem electric hot water system in a hallway cupboard of a Darling Point apartment, with the 22.11.13 install date written on the lid

The call from Darling Point was about a hot water system leaking from the top. Not dripping, spraying. It was a Rheem mains pressure electric tank in a hallway cupboard of an apartment, and the date it went in was still written on the lid in marker: 22 November 2013. By the time Greg opened the cupboard doors it had been working for almost 13 years, and the rust rings on the lid showed water had been escaping up there for a while before it got bad enough to notice.

Old Rheem mains pressure electric hot water system in a Darling Point apartment cupboard, with 22.11.13 written on the lid in marker and rust rings on top — The old Rheem with its install date, 22.11.13, still on the lid. The rust rings on top are where water had been getting out for some time before it started spraying.

Why a hot water tank leaks from the top

Water at the top of an electric storage tank usually comes from one of three places. The relief valve, which is designed to release a little water as the tank heats but shouldn't run or spray. A pipe connection that has corroded where it screws into the tank. Or the cylinder itself, which has rusted through near the top where the fittings go in.

The first two can often be repaired on a tank with plenty of life left. The third can't. Knowing which one it is matters, and on an older tank the rust on the lid is a strong clue.

Why this leaking hot water system was a replacement, not a repair

Inside every electric storage tank is a sacrificial anode, a metal rod that corrodes so the steel cylinder doesn't. Once the anode is used up, the cylinder starts corroding instead. Nothing in this tank's history suggested the anode had ever been checked, and at nearly 13 years it was well past the point where it would have been doing its job.

Even if the leak had been from a fitting, putting new parts on a tank that age means paying for a repair on a cylinder close to failing anyway. The honest advice was to replace it.

What Greg installed

Greg shut off the power and the cold water supply, drained the old tank and got it out of the cupboard. That's the awkward part in an apartment: a full electric tank is heavy, the cupboard is tight, and the floor around it is timber.

In its place went a new Rheem 250 litre electric, a twin-element unit that fits the same space. Greg fitted a new relief valve with a copper drain line and insulated the valve, then filled the tank, bled the air out, powered it up and checked every joint for leaks.

New Rheem 250 litre electric hot water system installed in a Darling Point apartment cupboard, with an insulated relief valve and copper drain line — The new Rheem 250 litre electric in the same cupboard, with a new relief valve, insulation and a copper drain line.

Hot water cupboards in Darling Point apartments

Most homes in Darling Point are apartments, and a lot of their hot water systems sit in internal cupboards like this one: off a hallway, next to timber floors, with another apartment below. A tank leaking in a garage or a side passage is a nuisance. A tank spraying water indoors on an upper floor is a problem for the floor, the cupboard and the ceiling underneath, which is why it's worth dealing with sooner rather than later.

It also raises the strata question. Under the NSW Government's common property memorandum, a hot water system inside a lot that serves only that lot is the owner's responsibility, while one that serves more than one lot, or sits outside any lot, is common property. Your building's by-laws can change that, so check them before assuming either way.

Norton Plumbing does hot water replacements across the eastern harbourside suburbs, including Darling Point, Double Bay and Edgecliff, as well as in the beach suburbs. See our hot water page for the systems we install.

Warning signs your hot water tank is near the end

Rust marks or water rings on the lid. Water is getting out at the top even if nothing is dripping yet.
A handwritten install date more than 10 years ago. Installers often write the date on the tank. If yours says 2016 or earlier, start planning.
A relief valve that drips all the time or never. A little water while the tank heats is normal. Constant running or spraying isn't, and a valve that never releases anything may be seized.
Rusty or discoloured hot water when the cold runs clear. That's coming from inside the cylinder.
Damp carpet, swollen skirting or a stain on the ceiling below, in apartments where the tank sits in an internal cupboard.

How to reach Norton Plumbing

Norton Plumbing has worked across Sydney's Eastern Suburbs since 2019, on hot water replacements and repairs, blocked drains, leak detection and general maintenance. I hold NSW plumbing licence 397768C, and Greg ran this job. The team works out of 10/11a-15 Berwick St, Coogee. If your hot water is leaking, see our hot water page or our Double Bay plumber page, or call 0477 858 951. Quotes are free across the Eastern Suburbs.

Frequently asked

Common questions

Why is my hot water system leaking from the top?: Usually one of three things: the relief valve releasing more water than it should, a corroded pipe connection where it screws into the tank, or the cylinder itself rusting through near the top. The first two are often repairable. The third means the tank needs replacing, and it's the most likely cause on a tank over 10 years old.
Can a leaking hot water tank be repaired?: It depends on where the water is coming from. A faulty relief valve or a leaking connection can usually be replaced. A cylinder that has corroded through can't be patched safely, because it's holding hot water under mains pressure. At that point replacement is the only real option.
What should I do if my hot water system is spraying water?: Turn off the cold water isolation valve at the base of the tank, which stops more water getting in. For an electric tank, also switch off the hot water circuit at the switchboard so the element isn't heating an emptying tank. Then move anything valuable away from the water and call a licensed plumber.
How often should the relief valve on a hot water system be checked?: Rheem's own label on this unit says to ease the relief valve lever at least once every six months, and to check or replace the valve at intervals of no more than five years. Easing it takes a few seconds, and it keeps the valve from seizing so it can still release pressure when it needs to.
Who pays to replace a hot water system in a NSW strata apartment?: Under the NSW common property memorandum, a hot water system inside a lot that serves only that lot is generally the owner's responsibility. One that serves several lots, or sits outside any lot, is common property. Your building's by-laws can change this, so check them first.

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