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Water Heater Noise: Why You Need to Listen

Updated
A noisy water heater can be an early warning of trouble brewing. Here’s what it could mean.

Most water heaters make at least some noise, but usually it is quiet enough to go unnoticed. If there are unusual noises coming from your heater, it’s understandable to get worried.

There are many reasons for your water heater making different sounds when hot water is turned on. Some of these are nothing to worry about but others could indicate a developing problem.

This article will help you get a better idea of whether or not there is a problem with your heater, and offers solutions to some common problems. It’s important to address any heater issues as soon as possible to ensure you can keep using hot water.


Causes and Noises

Here are some of the most common water heater issues along with the sound your heater might make when heating.

1. Tank Buildup

Sediments, mineral deposits, and other buildup can cause trouble inside your water heater. Sediment is broadly defined as any sort of material that settles inside your tank. It could be sand or other debris that enters the tank with the water, or minerals released as the water is heated.

Sediment buildup can start as a minor problem, only slightly decreasing your unit’s efficiency. However, as it continues to accumulate it can cause clogging to the point that you can’t even flush the tank — this could require a full replacement.

Rumbling

You will usually hear this noise as the temperature increases inside the tank. As the water expands, it passes the sediment — it’s this interaction that causes the rumbling.

The sound tends to grow louder as more sediment collects. If the noise has become very noticeable, the buildup may have reached a critical level.

How to Fix It

Flush and drain your tank. You can use a deliming solution to help get rid of the sludge. If you don’t like the thought of using chemicals, try white vinegar.

Popping

Popping noises are usually caused by limescale, a common problem in areas with hard water. The minerals (calcium and magnesium) are found in the ground and absorbed by the water as it passes through.

While these minerals are beneficial for our health, they can be harmful to a water heater. As the water is heated within the tank, the minerals separate and form limescale.

Loose sediment on the bottom of the tank can also be a factor. Sometimes steam bubbles are formed beneath the sediment. As the water heats up, the bubbles burst, hence the popping sound.

How to Fix It

Try draining and flushing the tank to remove any mineral sediment. If your tank has a heating element, descaling it may reduce further deposits.

Sizzling, Hissing, and Crackling

These are typical noises from an electric water heater but they could also indicate trouble. As sediment builds up at the base of the tank, the lower heating element can become covered or buried.

When this happens, it’s unable to heat the water or function properly and starts making noise.

How to Fix It

You need to drain the tank completely and remove the lower heating element. Soak the element in a descaling solution, then use a wire brush to gently remove any residue.

2. Fluctuations in Water Pressure

As the water pressure changes, you may notice a few noises. These are usually caused by the pipes and plumbing, rather than your water heater.

Ticking

A ticking noise is the most common sound caused by changes in water pressure. Many water heaters use water outlet and inlet nipples with heat traps. The nipples are what connects the plumbing to the unit — they essentially improve efficiency.

The heat trap can sometimes cause the ticking noises. If this is bothering you, you can simply replace the nipples with a non-heat trap.

Pipes and plumbing are also notorious for making noise. As the water leaves the unit through the pipes, they expand or contract as the water warms or cools.

When they expand, they could be rubbing against the structure of your house. Loose straps can also result in a ticking noise.

How to Fix It

Follow the sound and try to find its source. You might only need to tighten any loose straps. However, if the noise still occurs, you can install spacers that will prevent the pipes from moving.

Reducing the water temperature by a few degrees can also prevent the pipes from expanding too much. This could be enough to eliminate any ticking noise.

3. Condensation Leaks

Condensation is usually found in gas-powered water heaters. As the cold water is heated, it can create a significant amount of condensation. New models even use this to their advantage — they are called condensing water heaters.

As the gas leaves the exhaust, it is very hot. In condensing models, they reuse the condensation to further heat the tank. This results in less energy being used and a much cooler exhaust, which is better for the environment (1).

Sizzling

If you can hear a sizzling noise from your gas-powered water heater, you may have a condensation problem. As the water heats and condensation is formed, it could be dripping down onto the burners, sizzling as it hits. This could indicate a leak within the heater.

How to Fix It

Check the immediate area around the unit to see if there are any obvious signs of water. However, this is probably a job for your plumber.

4. Restricted Water Flow

The valves of your water heater system are what controls the water flow. If the flow is limited, you might hear a significant noise.

Whistling, Squealing, Screaming or Singing

As the water tries to flow through a small opening, you might notice whistling, squealing, screaming, or screeching noises. Certain valves could be the source of this noise issue:

  • T&P relief valve: The temperature and pressure relief valve is also known as a safety valve. It allows the water to escape if the pressure becomes too high inside the tank. If you suspect this valve is causing the issue, cut the power to your heater and call a plumber.
  • Inlet valve: It could be that the inlet valve isn’t fully opened — this can greatly restrict the water flow. Check the valve and make sure it’s open all the way.
  • Valves and lines: If you’ve checked the above and still notice some sounds, try inspecting the water lines and outlet valve. Check the lines for any flaws or kinks — the outlet valve should also be fully opened.

5. Water Source

Popping

An anode rod is an important component of a water heater — it helps prevent rust. If your local water supply is alkaline it could be causing a few problems inside your tank.

There are two main types of anode rod: magnesium and aluminum.

A popping noise is common if your water heater contains an aluminum type rod and is exposed to high levels of alkalinity. It’s believed that this type of metal reacts with the pH level of the water, creating a noise.

How to Fix It

If the aluminum anode rod is the problem, replacing it with a magnesium alternative might be the best solution.

6. Water Hammer

Banging, Knocking, or Hammering

Loud noises such as banging, knocking, or hammering are usually caused when the water is abruptly shut off. As it has nowhere to go, this causes the water to flow backward in your system. The resulting sound is often referred to as a Water Hammer (2).

It can potentially cause a water pipe to burst, creating a major problem in your home. It can also cause problems with your water heater.

Be Aware

Pressure could build. There may even be enough force to expand the tank shell. Damage to the flue tube and deformation of the tank are also possibilities.
How to Fix It

We recommend installing a water hammer arrestor (pressure reducing valve). This is a device designed to protect your plumbing, pipes, and tank by absorbing the shock created by the water hammer.

Tankless Water Heater Noise

Tankless water heaters aren’t known to create noises like tank models do. However, you may still hear pops or ticks or a sound like running water.

Clicking is common when the unit turns on and off. You might also hear other sounds if you live in a hard water area or if there is a buildup within the unit.

How to Fix It

Regular maintenance should help you stay on top of any unusual sounds.

FAQs

Why Is My Water Heater Making Noise?

Your water heater could be making noise for numerous reasons. It might be that your heater simply makes noise normally. If it has recently become louder and you’re concerned, it could be an issue with build-up of sediment in your hot water tank. This isn’t a major issue if addressed quickly, which can be easily achieved by flushing your system. It can also help to clean your anode rods, which struggle to work when affected by scale buildup.

How Do I Stop My Water Heater Making Noise?

This depends on what is causing the noise. The majority of noise from a tank water heater is caused by sediment buildup in the tank, which you can resolve by flushing the tank. Your anode rods, which are designed to draw sediment away from the rest of the tank, can become covered with scale. In this case, you will need to remove them and either clean them or replace them. Make sure the valves on the surrounding pipes are also open so water can flow freely.

Is a Noisy Water Heater Dangerous?

A water heater making noise is usually more annoying than dangerous, resulting from sediment in your hot water tank. However, if the tank becomes noisier and you ignore it, sediment can eventually build up so much that it prevents your heater from working properly. It could also be an issue with one of your valves not being fully opened, which can lead to pipes or your heater becoming damaged, so you should investigate this quickly.


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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.