Why your water heater sounds like popcorn

What makes the popping?

Ozarks water is hard. It picks up minerals from the limestone it runs through, and when the water heats, those minerals come out and settle on the bottom of the tank as sediment. On a gas unit the burner sits right under that layer. Steam bubbles form under the sediment and get trapped, and each one that breaks free is a pop. That's called kettling, and it's why a hot water heater sounds like popcorn while it heats.

The burner's heat has to get through that layer to reach the water, so a gas tank recovers slower and the gas bill creeps up. An electric tank collects the same sediment and makes the same kind of noise, and scale on its heating elements makes them run hotter and burn out sooner. Left alone, the layer keeps getting thicker and wears on the heater.

Which water heater noises are normal?

Ticking or clicking as the tank heats and cools is normal. It's the pipes and the heat traps in the fittings on top moving with the temperature. A light hum from an electric tank while it heats is normal too, and so is gurgling after a lot of hot water use, or a soft whoosh when a gas burner lights. A gas tank can also sizzle for an hour or two after it fills with cold water, mostly in winter and early spring. That's condensation dripping onto the burner, and it stops once the tank is hot.

Noises that need a closer look

If you smell gas, don't touch the heater or any electrical switch, and don't use a phone inside. Get everyone outside and call the gas company from there, or 911 if you can't reach them.

• When a water heater is making a squealing, screeching or whistling noise, water is often being forced through a tight spot, like a valve that isn't all the way open. Check that the shutoff valves on the pipes above the tank are open fully. On a power vent unit it can also be the blower, and on an electric tank a heating element going bad.
• A buzzing or vibrating noise from the water heater while it runs is often a loose part. Before anything gets tightened to stop the vibration noise, turn the gas control to off or switch off the heater's breaker, and let it cool. On an electric tank, the wiring behind the element covers is live until the breaker is off, and anything past snugging a loose screw is a job for a plumber.
• Sizzling or hissing that keeps up after the tank is hot can be a leak dripping onto the burner, or a leaking element gasket on an electric tank. Shut the heater down at the gas control or the breaker and have it checked.
• A bang or knock right when the washing machine or dishwasher shuts off is often water hammer in the pipes. A water hammer arrestor on that line usually takes care of it. If the pipe is loose or the house pressure runs high, strapping the pipe down or lowering the pressure helps too.
• A loud bang or boom when the gas burner lights usually means gas or fumes built up before the flame caught. Turn the gas control to off and call.
• Water or steam from the T&P relief valve pipe on the side of the tank usually means the temperature or pressure inside is too high, or the valve itself has failed. Stay clear of the end of that pipe, since what comes out can scald, and never cap or plug it. Turn off the gas or the power and call.

What if it sounds like water running?

If your water heater sounds like it's running, or you hear water running when no tap is on, look at the floor around the tank and at the end of the relief valve pipe. If there's water, shut off the gas or the power first, then close the cold water valve above the tank and call now. Water coming from the tank itself means the tank has to be replaced, though condensation on a cold tank can look like a leak for an hour or two. A drip from a fitting on top or from the drain valve can often be fixed.

Will a flush fix it?

If the tank is a few years old and the noise just started, usually yes. Draining the tank and flushing the sediment out quiets it down, and on a gas tank it gets some efficiency back. A. O. Smith and Rheem both call for a flush at least once a year, and more often on hard water like ours. Rheem says every six months.

Before draining, turn the gas control to off or switch off the breaker, close the cold water valve, and let the water cool, since it comes out hot enough to burn. Run a garden hose from the drain valve to a floor drain or outside, open a hot tap in the house, and then open the drain valve. Once it's empty, open the cold water valve with the drain still open to rinse out what's left. Close the drain valve before you refill, leave that hot tap open until water runs steady from it, and only then turn the power back on or relight the gas by the instructions on the tank.

On an old tank that has rumbled for years and never been flushed, the sediment can be packed hard, and flushing it can open a leak. The drain valve on an old tank can also clog halfway through or leak once it's been opened. On a tank like that, have it looked at before anyone opens the drain valve.

When it's time for a new tank

• The tank is 8 or more years old and noisy, especially if it has run on hard water and never been flushed.
• The noise keeps up even after a flush.
• The hot water comes out rusty, which can mean the inside of the tank is corroding.
• There's water or rust at the base of the tank, or the repairs keep stacking up.
• A big repair on a tank that old can cost a good part of what a new one does, and a new tank starts a new manufacturer's warranty.

The sticker on the side of the tank lists its size, and the serial number on it gives the age. Text a photo of it along with one of the base of the tank, and Joe will tell you whether a flush or a repair will do, or it's time to plan a new one. The water heater page covers repairs and replacements.

What a new water heater costs around Springfield: TheFatBook Cost Index.