We have been trying to find a leak in a common wall between two townhomes without any luck. The wall is always wet, and there has a been a gush of water (about 2-3 gallons only twice in the last year that we know of). We turned off the water and the water company said the gage was not moving. We had plumbers with camera in the drains look for leak. We have had structural engineers and water proofers. It doesn't happen after heavy rains or showers, flushing, or sink usage. The neighbor's air conditioner was checked and it's not leaking. The previous owner had this issue and never disclosed it and apparantly didn't find the leak either. We are opening up the walls to see if it's a pinhole in a copper pipe as some have thought, but still others think it's a leaky pipe underground. The neighbor's basement is 6 inches higher that this one. The previous owner put silicone in between the foundation and the rise to the neighbor's basement. The neighbor has not had any water issues. If any one has seen this before or can help, we'd greatly appreciate it! Thanks!