Late at night when all the TV and other house noises are off, I can hear the pipes in the bathroom knocking/popping in the walls and under the house (usually after a shower). Accompanying these noises, the water pressure in the bathroom sink surges (I shave after a shower). Also, I'll often hear sucking noises -- as if the pipes are gasping for air?

My local plumber can find no water leaks, and of couirse, when he's here the noises aren't present then. I seldom hear these noises or experience the surging during the daytime and it only occurs in the bathroom (not kitchen, etc.) I'm hesitant to call him back again or he might report me to the county mental health department.

Anyone with ideas?