[kathyt2009]

Every time I run the dishwasher, there is a rattling noise coming from the sink drain when it fills up. A few minutes later, there is a loud banging in the pipes, which continues intermittently throughout the cycle. Any ideas on what might cause these problems? Thank you!

[drtom4444]

You need to install an air chamber in the pipes to stop the water hammer. Install a T near the water heater on the hot and cold water lines the same size as those lines. Put the T inline with water lines with the stem of T going up with a cap on it. That's the air chamber that acts like a shock absorber. Problem solved.

[drtom4444]

Forgot to tell you: the pipe going up should be about a foot long.

[hkstroud]

Sound like you have two problems, a loose washer in a stop valve and water hammer.

A loose washer will cause fluctuation in the water flow and cause pipes to rattle. If this occurs at the kitchen sink only, the loose washer is probably in the hot water stop valve under the sink. It only sounds like it is coming from the drain.

Water hammer occurs when a fast acting valves shuts off and abruptly stops the flow of water which causes the pipes to bang against a structural member. Air chambers should have been and probably were installed on the pipes inside the walls close to the valve. Over time the air trapped in the air chambers is absorbed by the water and they are no longer effective. They need to be recharged with air.

Turn off the water to the house. Open all faucets and flush each toilet. Remove the valve stem of the hot water stop valve under the sink. The valve stem is removed by removing the handle, unscrewing the bonnet nut around the stem and then unscrewing and removing the stem. Inspect the washer and make sure the washer screw is tight. If it is with in your capabilities, it would be better to just replace the valve, especially if it is a compression fit valve which it probably is.

By the time you have repaired or replace the valve, your pipes should have drained completely. Close all faucets. Turn on water to the house. Open main valve only enough to hear water begin to flow. If you open a main valve to quickly you can blow out the cartridge of some single lever faucets. After you can no longer hear water flowing, open the main valve completely.

The air trapped in the pipes will be forced into the air chamber and they will function again, cushioning the sudden stopping of water flow.

[kathyt2009]

Thank you drtom4444 for your responses.