My water pipe is making a slight thumping sound. It's sort of like someone is very, very lightly tapping the pipe with a rubber mallet. It's very strange because I can't seem to locate exactly where the thump is.
- I have the hot/cold lines branch off at a T in the basement.
- The hot line does NOT have a shutoff except at the water heater and at the fixtures.
- Both lines travel ~15 ft to the left(kitchen) and ~8ft to the right before going vertical to the upstairs full bath.
- The 8ft run to the right includes a branch for the washer and a hose spigot outside (shutoff on spigot is in "off" position)
- At the T-intersection on the cold line, there are two ball valve shutoffs on each side of the T. (I had a leak on the joint late fall/early winter and took the chance to repair and add the shutoff valves.)
Is it the valves being so close to each other? I can't say for sure but it may have started after I put the valves in.
If not the valves, any idea what could be causing the thump? I can't actually hear it in the basement (where all of the pipes are exposed) so I suspect it's in the vertical run.
Is there air possibly stuck in the pipe? If yes, how do I get rid of it?
The thump occurs usually when there is no water running but I also hear it sometimes when the water is running.
There is no water hammer or pipe banging when I turn the water on or off.