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by CareyBot

Once again it’s time to empty the question bag. Today it’s a bit of a hodgepodge. Water and electricity usually don’t go together, but today is the exception.

Q: We must have air in our plumbing pipes, because every time we turn them on and then shut them off there is a big bang. After searching online for "air in pipes," I have discovered that we have a water hammer problem. The loud noise occurs only when we shut off any sink, or the dishwasher stops. Do you have simple, easy-to-follow instructions on how to get rid of the water hammer?

A: Maybe. Water hammer is hydraulic shock. It’s the sudden increase in water pressure in the pipes when there is a change in the direction or velocity of the water. Water is not moving in the pipes when all the valves in your water system are closed. The pressure is constant. When a faucet is turned on, the water flows. Depending on the water pressure, it probably moves at a pretty good clip.

When you turn off the faucet, the water flowing in the pipeline suddenly stops. The result is the transfer of energy created by the flowing water to the pipe walls, making the pipes shudder and vibrate. The pressure wave bounces back and forth, hitting the sides of the pipe until it dissipates because of friction. The pressure wave causes the banging you hear.

Try this simple fix: First shut off the water to the house at the main shutoff valve. That could be at the water meter. Next, open all of the faucets (sinks, showers and tubs). Go to the lowest water outlet. It will usually be a hose bib, but could be a laundry sink in a basement. Drain the system of water.

When all of the water is out of the system, close all of the faucets and turn the water back on to the house. With luck, it will eliminate the water hammer. Be careful when turning on the faucets, as they will spit air until the water refills the pipes.

(Our reader followed these steps and her water hammer is only a memory.) …CONTINUED