Rumbling Pipes When Water NOT In Use
When someone uses hot water, the hot water pipe expands, lengthwise also. (When someone uses cold water, the cold water pipe contracts.) Later the pipe returns to room temperature. Some of the holes in the joists or studs through which the pipe passes may be a tight fit and the wood deforms slightly as the pipe elongates or shortens. Exactly when the pipe slides slightly in the hole to relieve the stress is random and sudden and the jolt can be transmitted to other, looser, pipes that can rattle.
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.