Why Is My Water Heater Making Noise?

Popping or rumbling

Popping and rumbling are the most common water heater noises in Southern California. Our area has hard water, which leaves minerals behind as water is heated. Those minerals settle to the bottom of the tank and form a layer of sediment. Water gets trapped under that layer, boils and bubbles up through it, which makes the popping sound you hear.

Sediment makes the heater work harder, reduces how much hot water you have and can overheat the bottom of the tank. Flushing the tank can remove loose sediment. If the buildup is heavy and the tank is older, flushing may not help and replacement may be the better option.

Banging or knocking in the pipes

A loud bang when a faucet or appliance shuts off is often called water hammer. It happens when fast-moving water suddenly stops and sends a pressure wave through the pipes. It is not always caused by the water heater, but it can stress fittings and valves over time. Solutions include water hammer arrestors, a pressure regulator or a thermal expansion tank, depending on the cause.

Hissing or sizzling

On a gas heater, sizzling often means water is dripping onto the burner. That can come from condensation, a leaking fitting or a leak in the tank itself. On an electric heater, hissing can come from sediment around the heating elements. If you also see water around the heater, follow the steps in our leaking water heater guide.

A hiss coming from the temperature and pressure relief valve means it may be releasing pressure. That is a safety warning and should be checked right away.

Screeching, whistling or humming

A high-pitched screech or whistle usually means water is being forced through a partially closed valve. Check that the supply valve is fully open. Humming on electric heaters can be a loose heating element vibrating as water flows past it. Tankless units can make fan and clicking noises during normal operation, but new or louder noises are worth having inspected.

Noises that need a professional

Call a licensed technician if you notice any of these along with the noise:

• Water on the floor or dripping from the tank
• Discharge from the relief valve
• Rusty or discolored hot water
• Loud banging coming from inside the tank
• A burning smell or scorched area near the burner

Repair, flush or replace?

For many noisy heaters, a professional flush and inspection is all that is needed. We check the anode rod, test the relief valve and look at venting and burner condition at the same time. If the heater is older, has heavy sediment and is losing capacity, replacement may save you from a sudden failure. We will explain what we see and let you decide. For pricing on service or replacement, call for a free quote.

To keep sediment under control, many homes in hard-water areas benefit from annual maintenance. Our maintenance plans make that easy.

We're local and ready to help

The Water Heater Warehouse is based in Fullerton and services noisy water heaters throughout Orange County and nearby communities. Call and tell us what the sound is like and when it happens, and we will help you figure out the next step. It helps to note whether the noise happens while the heater is heating, right after someone uses hot water, or when a faucet shuts off. That timing tells our technician a lot before they arrive, and it often means the visit is shorter because the likely cause is already narrowed down.

Related service

Learn about our water heater maintenance and flushing, or see our water heater repair in Fullerton.

Frequently asked questions