When the upstairs toilet is flushed or when the shower in the same bathroom is running, I hear loud noises spaced about 5-10 seconds apart-sounds like clicking or ratcheting. It does not seem to be related to hot water since it happens when the toilet is flushed too, even if the shower has not been run recently-I changed out the plumbing in the toilet to a flowmaster but that made no difference. Also the noise starts a few seconds after the toilet is flushed i.e. as it is refilling-not sure I can isolate it to a drain pipe as opposed to the water pipes-drain pipe is pvc and the water pipes are the clear pex. Any help very much appreciated.