Here’s Why Water Heater Makes Noise When Hot Water Is Turned On

A water heater is one of the most essential yet least appreciated appliances in households cause it lives buried in the basement. We only realize its existence when you suddenly get cold water or you hear some sound coming out of it. 

For starters, these water heaters can make a range of different noises, and mostly each has different reasons. It’s possible to find out the cause and solution depending on the type of noise a water heater makes. So whether it’s time for maintenance and flushing or to replace some part, it’s all in that sound.

Today, we are going to talk about those most frequently observed noises, their cause, and possible solutions. So hold tight.

6 Types of noises water heater can make when hot water is turned on

1. Popping or knocking

Popping sound

The popping or knocking sound is very common with tank water heaters especially if you are living in a hard water region. What this noise intel is that there’s sediment like calcium and other particles has built up on the heating element. 

This sediment traps water within them. The water gets heated by the heating element and forms bubbles which on bursting makes a “pop” sound. However, the popping sound is not the only sign of sediment buildup. Usually, you will also notice an increased energy bill to heat the same amount of water as the sediment reduces heating efficiency. 

The solution to getting around this problem is to drain your water heater, descale it and do at least annual maintenance. Here’s a complete water heater descaling guide for both tank and tankless.

Another cause for popping sound could be the aluminum anode rod being exposed to too much alkaline water. Alkaline water reacts with an aluminum anode rod and makes that popping or knocking sound. In this case, you will need to replace your anode rod with a magnesium anode rod. You will want to call your plumber for this.

2. Screeching noise

Screeching sound

Now this sound is less of a water heaters effect but instead more of plumbing. Normally, when a water flow is restricted, it makes a screeching noise. 

You will want to check your water inlet and outlet valves if they are partially open and if they are then wide open them. 

Also, make sure the temperature and pressure relief valve is properly functioning. Located on the side of the tank with a long pipe, carefully pull the valve a little up. If it drips the water then it’s working otherwise you might need to replace it. 

3. Cracking, screaming, sizzling, or hissing sound

Hissing sound

If you hear your water heater making cracking or screaming noises and you have pinpointed the source to be your water heater unit then you are right. 

Water heaters, especially gas-fired unit, makes these cracking noises when condensation leaks and falls on the hot burner. 

You should also be able to notice small water puddles on the floor beneath your heater. 

Unfortunately, the solution to this is not usually DIYable and you will need to call a professional. 

Related: How to prevent the water heater from leaking.

4. Rumbling sound

Rumbling sound

When sediments stack up on the bottom of the tank and water starts to flow and flush in, the sediments hit on the walls of the tank, and in all this process creates that rumbling sound. 

Solution? Drain your water heater and perform regular maintenance.

5. Ticking sound

There can be various reasons for a water heater to make ticking noises. In fact, it’s not necessarily always the water heater to make this sound. 

Water pressure change, efficiency-boosting heat trap nipples located at the top of the tank, and even pipes due to loose straps can make these noises. 

Actually, there’s nothing wrong with the heating system in this situation. It’s just noisy. And if it irritates you then what you can do you minimize the ticking is:

Tighten the pipe straps if those are loose. Or you can also change the heat-trapping nipples with dielectric non-heat trapping nipples.

6. Banging or humming or hammering sound

bang or humming
Banging hammering noise

Does it make a sound from the inside of the tank like someone’s banging or humming? 

Such a noise occurs when water is suddenly forced to stop or change its direction. It builds pressure in the system.

This pressure can be damaging and can burst pipes, expand tanks or even deform them. 

The solution to this is simple. Call your plumber and get a water hammer arrester installed. 

Clicking noise from your tankless water heater noises? 

tankless water heater making noises

To be honest, tankless water heaters don’t make much noise and usually are quieter than tank-type. 

If you hear a clicking sound from the unit then it’s coming from the flow switch. It activates and lets water flow through the heat exchanger when a tap is opened. Flow switch controls the flow of water and makes that click in the process. So it’s completely normal and has nothing to do about it. 

If you have a gas-fired water heater and a hearing fan whirling then it’s the seemingly dusty fan that needs cleaning.

Frequently asked questions

Why does my tankless water heater make noise?

Depending on the type of noise it’s making, there can be a variety of reasons why your tankless water heater making noises. For example, the flow switch makes a clicking noise which is normal. The dirty fan can make a loud whirling sound. 

How do I stop my water heater from making noise?

If your water heater is already making noise then the best will be to find out the cause and fix that. If you are not able to do that yourself then you better call a professional plumber. 

To prevent the water heater from making noises, always do regular maintenance and flushing of your unit.

What kind of noise does a tankless water heater make?

Tankless water heaters don’t make as much noise as does tank-type do. You can hear noises like clicking, fan whirling, and vibration from your tankless water heater


I hope this article helped you in finding out what’s wrong with your water heater. If you still can’t figure out or none of the above sounds match what you are hearing, then I advise you to call your plumber. 

All in all, always get annual maintenance done to keep your home water heating system working smoothly and free from problems.

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