Why is dishwasher so noisy when pumping hot water into load?

Question

the dishwasher is <2 years old and when it is on and pumping hot water into the load, it makes a loud banging noise (2-3 times per load for about 10-15 seconds each time). when i look under the sink it is the water pipes that are vibrating violently making the noise. any suggestions?

Answer 1

You are experiencing water hammer, caused by the lack of an air cushion in the water pipes or there may be a pipe that is not securely fastened to a wall stud and it rattles when the water is shut off. This can be fixed by locating the pipe that is banging and using a pipe strap to fasten it securly.

Banging can also result when water, with no air in the pipe to ease the shock, slams into the closed valve. It is sometimes possible to cure water hammer by draining the water out of the pipes and admitting some air.

In most homes, the water can be drained by closing the valve on the street side of the water meter and loosening the union fitting on the other side of the meter. All hot- and cold-water faucets in the house should be opened to let the water drain out. When draining stops, close all the faucets, retighten the union fitting, and open the water valve.

If the house has well water or you are in doubt about how to drain the lines, have a plumber do it.

Another treatment, which might be needed if draining doesn&#039;t work, is installing an air-cushion chamber in the noisy line. The chambers, which are available from plumbers and plumbing-supply dealers, are generally installed above or near noisy fixtures. Pieces of capped pipe 12 to 18 inches long are also sometimes used for air chambers and are easily installed on the water heater inlet and outlet pipes.