I live on the 11th floor of a multi-unit building. Over the past year a humming from the main water pipe that runs straight up through the building has gotten much louder. We recently re modeled out kitchen 2 years ago. The noise wasn't there before, and it didn't show up directly after the remodel. The building maintenance people turned off the motor that pumps the water up through the pipe to all the units. The noise went completely away. The noise can be heard from other "06" units above and below us, but not nearly as loud. We have a 2x2' hole behind the slide-in stove where we can see / touch the water pipe. It definately is the vibration. The ceiling and floor are concrete, and the humming travels through out the entire condo. It's very loud, and driving us nuts. We tried seeing if anything was touching / vibrating on the pipe, and nothing is (from the hole behind the oven).

What would be our next step? Does anyone have any ideas? Any advice would be fantastic.