That sudden banging from your hot water cupboard at 2 am isn’t just annoying; it’s your system talking to you. And it’s actually a common occurrence for Australian homeowners. If you’ve been hearing strange noises coming from your hot water system, you’re probably wondering if it’s something that needs to be dealt with urgently or if you can keep procrastinating on it.
This guide will help you understand what the different sounds mean: the hums, bangs, pops, and whistles coming from your system. We’ll cover the different Australian systems, from electric and gas storage to continuous flow, and give you clear advice. By the end, you’ll know if it’s a quick DIY fix or time to call in the professionals.
While some sounds are simply part of normal operation, like the quiet hum of a heating element, others spell trouble on the horizon.
The type of noise and its cause often depend on your system, of which there are four main types:
For example, an electric storage heater can start rumbling from sediment buildup, a common occurrence. Another common one is a gas continuous flow unit that whistles due to pressure issues. Heat pumps have fans and compressors that add their own operational sounds.
The most common reasons across all systems include:
Let’s break them down.
Use this noise reference guide to quickly decode what your hot water system is trying to tell you. Understanding these sounds early can give you peace of mind and help you prevent minor rattles from becoming major repairs.
You might hear a single loud bang or rapid knocking, likely occurring right as you turn off a hot tap.
The most common cause is water hammer, which is a pressure shockwave within your pipes. But sometimes we find it can be loose pipe mounting or a failing pressure regulator. It’s actually not an immediate emergency, but repeated shockwaves stress pipe joints and fittings.
You can check for loose pipes yourself, but for proper diagnosis and to install water hammer arrestors to prevent potential damage, you’ll want a professional call.
Severity: Moderate
A popping or crackling sound during the heating cycle is a classic sign of sediment build-up. It happens when minerals from hard water settle and harden at the bottom of the tank. As the heater operates, steam bubbles erupt through this layer.
This is very common in hard water regions like Adelaide or parts of Queensland. While not an emergency, it does reduce efficiency. A DIY tank flush can help. However, if the noise continues, the sediment may be cemented on and require professional descaling.
Severity: Moderate
Are you hearing a steady, low-frequency hum or a physical vibration? This is likely a mechanical cause and mostly occurs in electric storage systems where a loose heating element can vibrate at mains frequency. A low hum is often just an annoyance. But a loud hum requires a licensed professional to inspect and tighten or replace the element safely.
In continuous flow units, a faulty solenoid valve can also hum. However, high water pressure can also cause pipes to resonate in any system. What to do? Firstly, check if the unit is securely mounted. If it is, test your home’s water pressure. If it persists, call in a pro.
Severity: Low/Moderate
True to its sound, a high-pitched whistle or screech is one of the most urgent sounds your system can make. It means there’s excessive pressure forcing water through a restricted opening, most commonly a faulty or partially open Temperature Pressure Relief (TPR) valve.
This is urgent, as a failed TPR valve cannot relieve dangerous pressure buildup. If you hear this, turn your water off and call a licensed plumber immediately for replacement.
Severity: High/Urgent
Hearing a deep, kettle-like rumbling sound? This is a more advanced sediment problem where the mineral layer has become so thick that water becomes trapped underneath. As a result, the bottom of the tank overheats, causing the trapped water to boil and steam (creating the rumbling noise).
In our experience, this means your system is nearing the end of its life. While professional servicing for a full flush is essential, for older units, you might want to look at a full replacement.
Severity: High
Like air escaping a balloon, a steady hiss usually indicates escaping water or air from a leak. It could stem from a valve or a pipe connection. The worst-case scenario is a pinhole leak in the tank itself.
Locate the sound and look for visual clues such as drips, moisture or rust trails (especially around the TPR valve pipe or the tank base).
A small valve leak is fixable. However, moisture from the tank usually means imminent failure.
Severity: Moderate/High
Important: if you have a gas system and hear a hiss and smell gas, treat it as an emergency: turn off the gas at the meter, open doors and windows, and call a gas fitter immediately.
Light, metallic ticking or tapping is usually harmless thermal expansion. What happens is that the tank and pipes heat up and cool down, they expand and contract, often making ticking sounds where they contact mounting brackets. It only becomes a concern if the ticking escalates to a loud knocking. For standard ticking, simply monitoring is sufficient.
Severity: Low
You may hear this after using hot water when air is trapped in the pipes, or water percolates through sediment as the tank refills. Air can enter the system after maintenance or if there’s a minor cross-flow issue. You can often purge air by opening the highest hot tap in your house and letting it run.
However, constant or loud gurgling, especially with air spurting from taps, means a problem with the inlet or pipework that requires a professional diagnosis.
Severity: Low/Moderate
The following sounds are red flags that demand more than just a listen. They require prompt professional help.
Certain noises should prompt you to pick up the phone, including persistent loud banging that shakes pipes, continuous hissing you can’t locate or high-pitched whistling or screeching from the temperature-pressure relief valve.
It’s not only noises that provide warning sounds. If you notice discoloured or rusty water, a suddenly reduced hot water supply, or visible corrosion on the tank or valves, your problem is advancing.
Additionally, if your system is over 10 years old and starts making new noises, it’s often a sign of significant wear, not just a simple fix.
If you’re experiencing frequent pressure relief valve activation (dripping or discharging water), you could have a dangerous pressure buildup.
This one’s worth repeating: for gas hot water systems, any unusual noise, especially a hiss or smell of gas, must be treated as a potential gas leak. Turn off the gas at the meter, ventilate the area, and call a licensed gas fitter immediately. Similarly, a buzzing sound near the electrical connections requires an electrician.
Do not attempt DIY fixes on either of these.
Attempting DIY repairs on these often voids your system’s warranty and may breach Australian plumbing and gas safety standards. Any repairs involving pressure, gas, and electrical connections must be completed by a licensed plumber or gas fitter to ensure safety and compliance.
Recognising these signs early can save you from a costly emergency repair or a system that’s not working at all.
The best way to avoid these concerning sounds is through proactive prevention. At Same Day Hot Water Service, we advocate for regular maintenance and smart system care. Our customers with the fewest issues are those who practice a little attention. It silences most noises before they start.
Stick to an annual professional service as a cornerstone of care. We know you might think of it as an extra cost, but it can save you money in the long term. It also aligns with good practice recommendations within the Australian plumbing industry.
At the very least, DIY maintenance. This means every six months:
If you live in a hard water area, which is common across much of Australia, managing mineral content is key. There are products you can buy from your local hardware store, such as a water softener to reduce scale formation. Or, you can install a sediment filter on your main water line.
If you have an electric storage system, a routine tank flush (draining a few litres from the drain valve) every six months can prevent sediment from accumulating and hardening.
Unfortunately, there are some unlicensed workers out there not installing systems correctly. Always make sure you go with a professional. They will ensure:
Finally, understand your system’s typical lifespan (8-12 years for many storage models). You can check this on the manufacturer’s website. Planning a proactive replacement before a major failure is the ultimate form of preventive maintenance.
Most hot water system noises come down to routine maintenance needs, but some are urgent warnings. If something sounds off, when in doubt, get a professional assessment.
After all, the cost of early intervention is always less than an emergency breakdown.
At Same Day Hot Water Service, our licensed experts have the experience to diagnose and repair all system types across Australia quickly and correctly.
Hearing a warning sign? Or is your hot water system beeping? Call us on 1300 721 996 for fast, reliable service you can trust.
Common hot water system noises typically signal specific issues: banging often indicates water hammer or loose pipes, popping points to sediment buildup, whistling warns of dangerous pressure, and hissing suggests a leak.
A new or unusual noise usually means a component is failing, such as a build-up of scale, a faulty valve, water flow pressure, loose elements, internal corrosion or a faulty hot water tap.
Yes, you should investigate noisy hot water systems; while some strange sounds like light ticking are normal, others like whistling, rumbling, or persistent hissing indicate serious or urgent problems requiring professional attention, especially when dealing with gas or electric systems.
A loud, continuous noise, like rumbling, screeching, or a loud hum, often signals a severe issue such as major sediment overheating, a critical pressure fault, or a failing heating element, which needs immediate assessment.