We have a townhouse that we've lived in for about 1 and 1/2 years. Over the past few weeks, there's been a very loud vibration coming from the wall that supplies water for both the upstairs bathroom and the downstairs bathroom. You can actually feel the shower head vibrating. It's extremely loud and will fade in and out. It is random, and will occur when no water has been used. It seems to be increasing daily and happening during the day, and in the middle of the night. When it occurred the other day for a long period, we went to the basement to see if we could isolate a pipe. When we grabbed the hot water pipe in the basement, you could also feel the vibration in your hand. What could be causing this, especially when no one is using any water and nothing is running (hot water tank, water softener, etc.) This is driving us nuts! It's soulds like the whole house is vibrating. Thanks!