We have noticed a humming noise when both the hot and cold water supply lines are turned on, but not when it is just the cold water or just the hot water. Any ideas as to what is going on and how to fix it?
1) I checked the pipes in the access panel. They vibrate, which is probably why we hear the hum.
2) The plumbing and fixtures are fairly new. They were installed as part of a home renovation 3-4 years ago.
3) The tub has a single spigot with separate controls for hot and cold water and I believe was made by Kohler. I have not been able to figure out how to disassemble to get to the valve stem.