By James Dulley
Dear James: Whenever I shut the water off quickly, there is a banging sound. I am building a new house and want the plumbing to be quiet. What can I do to stop the banging noise? — Kenny T.
Dear Kenny: A banging noise in plumbing has several possible causes and you should be able to avoid it in the house you are building and stop it in your present house. The noise is called water hammer and it is caused by a pressure shock in the plumbing when you turn off the water at a faucet, flush a toilet, a dishwasher or clothes washer stops, etc.
The water pressure at your house is probably unusually high making the noise more pronounced. Higher water pressure creates a stronger shock wave inside the pipes when the water flow is abruptly stopped.
The water pressure in a house is determined by how much higher the water tower is than your house. If you live near the bottom of a hill, there will be a greater elevation difference between the water tower and your house. A water pressure around 60 psi is considered to be a good target and should not cause water hammer in most homes.
Since your new home is not complete yet, consider installing 3/4-inch water lines instead of standard 1/2-inch lines. With the larger diameter pipes, the water velocity inside the pipes will be slower. This not only reduces the possibility of water hammer, but it also will make your plumbing quieter overall throughout your new house.
If your water pressure is on the high side, install a pressure-reducing valve where the water main enters your house. This is an adjustable valve that allows you to set the water pressure as low as you prefer. If you set it low, there will be less overall plumbing noise, but the water will not flow as fast from the faucets.
You might consider installing a pressure gauge at the pressure-reducing valve. It is not really necessary, but it certainly makes it easier to monitor what is causing plumbing noise. If the gauge shows the pressure is low enough and you still have problems, you may have to contact the plumber or builder.
Installing an expansion tank in the plumbing is a necessity today and having one probably would have stopped your water hammer in your existing house. New homes have a check valve in the incoming water line to keep water from your house from backflowing into the water main. This keeps the entire water main from become polluted there are problems in just one house.
An expansion tank is a small football-shaped tank that is half-full of air. This takes care of absorbing the shock when the fast flowing water is suddenly shut off to stop water hammer. It is often located somewhere in the utility room or basement near the water heater.
Another important purpose of the water expansion tank is to take care of volume changes of the water inside your house. As the water warms up inside your house plumbing, its volume expands.
With the water main check valve in new homes or with an add-on pressure-reducing valve in older homes, the water expands into the expansion tank. Without the tank, the water pressure builds up and may cause faucets to drip and other problems.
Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.