I have similar problem in my house. There is moisture on the wall where the water main enters thru the wall. Somebody raised a question: is it ground water or a pipe leaking? Good question, but how to find out if pipe is at least 4 feet deep in the ground and has a porch concrete slab sitting on a top of it. I figured that if it was a bad leakadge in the pipe, water would be showing up at much higher rate than just few drops. It is under pressure in the pipe, right? If this is a case, Home Depot and Lowes has a waterprofing stuff that hardens even under water. You all think I can use it?