Hot Water
Why is my hot water system making noise?
A noisy hot water system is usually sediment on the tank bottom, which rumbles or crackles as the burner or element heats water trapped underneath. Other noises include ticking from pipes expanding, a hissing relief valve, and banging water hammer in the pipes. Most are harmless, but rumbling and hissing are worth a service.
Rumbling or kettling: sediment on the bottom
The most common hot water noise Terry gets called about is a deep rumble, gurgle or popping sound, sometimes called kettling, that shows up while the system is heating. That's sediment. Over years, minerals and grit settle to the bottom of the tank and form a crust. Water gets trapped under that layer, heats up, and pops as it bubbles through, just like a kettle coming to the boil. It isn't dangerous on its own, but it's a sign the tank is working harder than it should, and it can shorten the life of the element or burner underneath. A flush can clear lighter sediment. On an older tank that's heavily crusted, it can be the start of the end.
Ticking or tapping: pipes expanding
A gentle ticking, tapping or clicking that comes and goes as hot water runs is almost always thermal expansion. Copper pipes expand slightly as hot water passes through, and they rub against the timber or brackets they sit on, which makes a tick. That's harmless. If it's annoying and the pipe is accessible, it can sometimes be cushioned, but it's not a fault and nothing to lose sleep over.
Hissing or trickling: the relief valve
A hiss or trickle near the pressure and temperature relief (PTR) valve, or the drain line running from it, is one to understand properly. Some discharge from the PTR valve during heating is normal expansion doing its job. A constant hiss, or a steady stream running from it, is not normal, and usually means the valve is worn or the water pressure is too high. That's one to get looked at, both to stop the water waste and because the PTR valve is an important safety device. A licensed plumber can test the pressure and replace the valve if needed.
Banging: water hammer
A bang or thud in the pipes when you shut off a tap is water hammer, the shock of fast-moving water stopping suddenly. It's more about the plumbing than the hot water unit itself, but the system often cops the blame. Left alone, repeated water hammer can loosen fittings over time. It's usually cured with a hammer arrestor or by securing loose pipes.
Roaring or whistling: a gas burner issue
If you run a gas system, storage or continuous flow, and you hear a loud roar, whistle or resonating hum when the burner fires, that's a different story to the tank noises above. A dirty burner, a partly blocked flue, or a gas pressure problem can all make a burner run rough and noisy. Unlike sediment rumble, this one isn't cosmetic. Because it involves combustion and the flue, it should be looked at by a licensed gas fitter rather than left to sort itself out.
Which noises need a plumber?
As a rough rule: ticking and the occasional expansion sound are harmless. Rumbling and kettling mean sediment and a system under strain, worth a flush or a service. A constant hiss or stream from the relief valve, and persistent banging, both deserve a look. If a noise is new, loud, or paired with leaking or a drop in hot water, don't leave it. Terry can listen to what it's doing and tell you whether it's a flush, a valve, or time for a new unit.
If your hot water system has started making a noise you don't like the sound of, call Terry on 0415 274 542. Fixed price quoted before any work, across Berala and Western Sydney.
Frequently asked questions
- Is a rumbling hot water tank dangerous?
- A rumbling tank is rarely dangerous, but it's a clear sign of sediment build-up making the system work harder. Left for years, it can shorten the tank's life and reduce hot water capacity. A flush often quietens it. On a very old tank, it can signal replacement is near.
- Why does my hot water system make a ticking noise?
- Ticking or tapping is usually pipes expanding and contracting as hot water flows through and rubs against brackets or timber. It's harmless thermal movement, not a fault. If it bothers you, an accessible pipe can sometimes be cushioned, but there's nothing to fix inside the unit.
- Should water come out of the relief valve?
- A little discharge from the PTR valve while the system heats is normal expansion. A constant hiss or steady stream is not, and points to a worn valve or excess pressure. That one needs a licensed plumber to test the pressure and replace the valve if required.
- Can I stop water hammer myself?
- Some water hammer eases if you secure a loose, accessible pipe, but the reliable fix is a water hammer arrestor fitted on the line, which is a plumbing job. If banging pipes are rattling your walls, Terry can find the cause and fit the right fix.
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Terry's been sorting plumbing across Berala and Western Sydney since 1986. Call 0415 274 542 for a straight answer and a fixed price.
NSW Licence L10959 · 40+ years experience