Why is My Hot Water Heater Making Noise When Water is Off?

It can be quite disconcerting to hear your hot water heater making noise when water is off. It doesn't matter whether it's an unusual pop, a strange hiss or constant ticking noises, these uncharacteristic noises will likely leave you thinking your hot water system isn't quite right.

Thankfully, some of these sounds will actually be fairly normal. For example, some storage water heaters may make noise while in the heating process. However, others suggest an accumulation of sediment, a faulty heating element, or changes to water pressure. In these instances, sweeping these noises under the proverbial rug can result in bigger dilemmas like damage to your pipes or hot water tank.

Ultimately, understanding the causes of these noises is the first, all-important step towards a safe, efficient and fully-functional hot water system.

So What is Normal for Water Heaters?

It’s important to understand that not every sound from your hot water heater is necessarily a problem. You’ll find that some seemingly unusual sounds are actually common water heater noises that can kick in during the heating process.

As an example, a mild hum or a gentle ticking sound can occur while the heating element turns on or as the metal components of the hot water storage tank expand and contract. Both gas and electric water heaters can make different sounds due to their power source, however, both may make soft noises during their normal operation.

The key factors are the volume of the noise, the regularity with which it happens, and whether the noise stops when you shut off the flow of water. Should you find the noise getting louder or more frequent, we recommend having a licensed plumber examine it before things get significantly worse for your hot water system.

Top Reasons Your Hot Water Heater Is Making Noise

If your hot water heater is making noise when water is off, there are several common reasons behind it. As we know, some of these sounds can be harmless. But others could be a red flag alerting you to the need to have someone take a closer look at your hot water system. Here are some of the most likely causes:

• Sediment build-up at the bottom of the tank may cause popping sounds or crackling noises.
• The system’s heating element may be loose and vibrating against the tank.
• A bad or sticking pressure relief valve is releasing air or steam.
• There may be excessive water pressure or sudden changes in water flow.
• Water hammer from connected pipes banging against surfaces.
• Steam bubbles may escape through layers of accumulated sediment.
• Loose pipe straps rattling as the system heats up.
• A damaged temperature valve might cause sizzling or hissing sounds.
• A faulty gas burner on gas water heaters or wiring issues in electric heaters.

If you hear any of these noises regularly, it’s worth calling a licensed plumber to check over your hot water heater to make sure everything’s working right.

The Common Effects Of Sediment Build-up

Óne of the most common reasons you might find your hot water heater making noise when water is off is sediment build-up.

If you have a storage hot water system, you’ll find that over time, minerals in your water supply can settle at the bottom of the tank. This is especially true in areas with hard, cold water. As the heating element warms the water, trapped steam bubbles push through the sediment. This typically causes loud popping sounds, crackling noises or even a low rumble. The build-up of sediment in your tank can reduce energy efficiency, shorten the life of your hot water system, and cause uneven water temperature.

The last thing you want to do is ignore the need to clear out the sediment from your hot water system. Doing so can also lead to rust build-up, possibly block the drain valve or cause damage to internal components. Regular maintenance helps remove sediment buildup and prevents more serious issues down the track.

Water Hammer and Pipe Vibration

Ever heard a loud hammering sound echoing through your pipes? It’s called water hammer and it is usually caused by an abrupt stop or change in water flow.

As water moves fast through your pipes and reaches a closed valve, the pressure forms a shockwave that causes your pipes to vibrate. Should you find strange noises coming from your water heater when water is off, this could be your primary suspect, particularly if the noise comes from nearby connected pipes.

Water hammer can gradually cause a raft of potential water heater issues, including:

• damage to fittings
• leaks
• loosened pipe joints

So, how to address the problem? Installing a water hammer arrestor or a pressure-reducing valve can be an effective way to absorb the shock and protect your hot water system.

Heating Elements and Hissing Sounds

Another all-too-common reason why you might find your hot water heater giving off a hissing noise or a sizzling sound is an issue with the heating element. This problem can be especially prominent in electric hot water systems.

Over time, accumulated sediment can coat the heating elements. This can trap water, resulting in the formation of steam. As the element heats up, that trapped moisture turns to steam, which in turn creates the sound. If your heating element is loose, that too can also vibrate against the tank and create a low humming noise. In some situations, you might also find electricity supply issues or moisture landing on the hot parts of the system responsible for these unusual sounds.

If the noises become persistent or louder, we recommend booking a professional plumber to inspect the system and make sure everything works as it should. Speaking of plumbing professionals…

When to Call a Professional Plumber

As we know, not every strange noise coming from your hot water heater spells trouble. However, some do need a closer look from a professional plumber. If you do not possess the appropriate licence, it’s actually illegal to carry out most plumbing work yourself, so calling a licensed plumber is your safest approach in more ways than one.

If you notice persistent noises or hissing sounds, or your hot water heater is making noise when water is off more often than usual, any of these could signal a bigger issue with your system. Always be on the lookout for the following signs, and act quickly:

• water pooling near the unit
• fluctuating water temperature
• a leaking gas line

Problems with the pressure relief valve, heating element or signs of sediment build-up can all affect how your hot water system works. A licensed plumber can safely diagnose the issue, repair it and make sure everything is working properly and safely.

Keep Your Hot Water Heater Running Smoothly

If you’ve noticed your hot water heater making noise when water is off, don’t ignore it. While some sounds are harmless, others could signal a variety of issues that need urgent attention.

Your hot water system works hard every day, and strange or persistent noises might be its way of asking for that attention. Regular maintenance, checking for water pressure problems and keeping an ear out for hissing noises or popping sounds can prevent bigger issues down the line.

When in doubt, call a professional plumber to inspect the system. It’s the best way to keep your hot water heater safe, quiet and working properly.

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