How to stop a water heater from making noise
Most water heater noise comes from sediment, the mineral grit that drops out of hard water and settles on the bottom of the tank. When the burner or element heats the water, the water trapped under that layer boils and bubbles up through it. That's the popping, rumbling, or crackling you hear. You can stop most of it by flushing the sediment out, and it's a job most homeowners can do on a free morning with a garden hose and some patience.
Figure out which noise you're hearing
Not every sound means the same thing, so it's worth listening before you start pulling hoses out.
- Popping, rumbling, or crackling while the tank heats up: This is sediment. It's the most common cause, and flushing will usually fix it.
- Ticking or creaking when the water heats or cools: The metal tank and pipes expand and contract with temperature. This is normal and usually harmless.
- A high whistle or hiss: Water is forcing its way through a small opening, often a partly closed valve or a mineral-clogged inlet. Flushing may help, but if the hiss continues, have a plumber look at the valves.
- Banging when a tap is shut off: That's water hammer, a shock wave in the pipes. It's a different problem with a different fix, so don't expect a tank flush to solve it.
If your noise is the popping or rumbling kind, keep reading. That's the one you can usually handle yourself.
Flush the sediment out of the tank
Set aside about an hour, and give the tank time to cool first. If it's been running, the water inside can scald you, so it's safer to wait a few hours after shutting off the heat.
- Shut off the power or gas. For an electric heater, switch off the breaker. For gas, turn the control to the pilot or off setting.
- Shut off the cold water supply. The valve is on the pipe going into the top of the tank.
- Open a hot tap somewhere in the house. This lets air into the system so the tank can drain.
- Attach a garden hose to the drain valve. The valve sits near the bottom of the tank. Run the other end of the hose to a floor drain, a utility sink, or outside where the water can flow safely.
- Drain the tank. Open the valve and let the water run out. Sediment may come out as a gritty sludge, which is exactly what you want to see.
- Stir up the bottom and drain again. Open the cold supply for a minute or two while the drain is still running. This churns loose sediment toward the outlet. Shut the cold supply and let the tank drain again. Repeat until the water runs clear.
- Close everything up. Close the drain valve, remove the hose, and close the hot tap.
- Refill the tank. Open the cold supply and let the hot tap run until the water flows steadily without sputtering. That tells you the tank is full of water and the air is out.
- Turn the power or gas back on. Give it an hour or so to heat up, then listen.
If the drain valve clogs with grit, or it drips or won't close fully after you've used it, don't force it. A valve that won't seal is a job for a plumber.
If the noise is still there
Some tanks have so much buildup that one flush doesn't clear it. Repeat the flush once or twice a year, and you'll keep the sediment from setting up hard on the bottom.
Lowering the thermostat can also help. Setting it to about 120 degrees Fahrenheit slows down how fast sediment forms and reduces how hard the water boils under it. It's also a safer temperature for showers and sinks.
If the noise persists after a couple of thorough flushes, the tank may be too far gone for flushing to help. Older tanks with heavy scale can keep rumbling even when clean, and at that point replacing the heater is often the more practical choice. A plumber can tell you whether repair or replacement makes more sense for your unit.
When to stop and call a professional
Flushing is a reasonable homeowner job, but a few situations call for a licensed plumber. Stop and call if the drain valve won't close, if you smell gas or see a gas burner that won't light properly, if there's water leaking from the tank itself, or if the noise changes suddenly into a loud banging or a hiss you can't track down.
If you've flushed the tank and the noise hasn't gone away, reach out to Joe's Plumbing. We can check the tank, the valves, and the expansion tank, and tell you plainly whether the heater can be fixed or whether it's time to replace it.