If you have a tank water heater that attaches to the hot-water system in your home, then you may notice that the appliance makes some noises as it runs. Humming and the sounds of water flowing in and out of the tank are normal sounds. However, there are other types of noises that may signify an issue with the tank. Banging is a common noise you may hear, and your water heater might need a bit of maintenance if the sound is noted. Keep reading to understand what the sound means and how it can be stopped.

Banging Noises and Check Valves

Banging noises can often be heard coming from your water heater when you use hot water and then turn off the water faucet. The banging sound comes from a small valve that sits inside the warm water supply pipe. When you turn off the hot water, the fluid that remains in the water pipe will begin to flow backward toward your water heater. To keep the water from entering the tank and air from building in your pipes, a valve will close once water starts to flow backward. The valve is called a check valve. Check valves are hinged devices that are typically made out of steel. The hinge opens the valve when water moves out of the water tank, and the hinge closes as water moves backward. Check valves that are in good condition will close silently, but they will start to make a banging noise as they close when the hinge begins to wear out. If you hear a banging soon after you turn off a hot-water faucet, then the noise is likely coming from the check valve. 

A noisy check valve is in poor condition and likely to fail at some point. To prevent water from flowing back into your water heater, replace the check valve. This valve is a T-shaped attachment that sits on the water outlet pipe close to the water heater. If the appliance also has a hot-water shut-off valve, then the check valve will likely be close to it. You can remove the check valve with a plumbing wrench. If you do decide to replace the valve, make sure to look at the flow arrow on the valve before installing it. To work correctly, the arrow on the valve should match the flow of water through the valve.

Heat Traps

If you do not want a check valve that may fail in the future, then you have the option of having something called a heat trap installed instead. A heat trap is a section of piping that uses gravity to keep water from flowing back into the water heater. The piping will look like an inverted U as it comes out of the heater. The hot water will be sucked up and over the U when you turn your hot water faucet on. When you turn the water off, hot water will be unable to make it back over the U, and this stops the fluid from flowing into the water heater again. 

Heat traps can be created with copper or PVC piping. You can also purchase some flexible piping to create a U shape. If you want to construct a flexible heat trap on your own, then purchase a length of crosslinked polyethylene (PEX) tubing or a piece of corrugated steel piping. Corrugated steel piping is often easier to use than PEX tubing because it can bend easily into the shape you need. When purchasing the steel piping, make sure both ends are fitted with screw-on attachments. The attachments will be able to connect to the tapers on the water heater and the present water lines. 

When you have the right pipe, turn off the water heater and use your plumbing wrench to twist off the section of piping that connects the hot-water tank to the check valve. Remove the check valve as well. Screw the tapered ends of the new pipe into place on the water-outlet pipe and onto the water heater. Afterwards, bend the pipe into an inverted U, making sure that the top part of the U sits above the long outlet pipe. This will help to make sure that water does not flow back through the pipe. Turn on your water heater when you are done. 

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