clogged shower drain -- poss. shaving cream. drano?
Our 1 year old shower drain is clogging up (water is draining much slower than it used to). DH uses shaving cream every day in the shower. Now we're noticing a 1/2" thick chalky-like build-up in the drain pipe and we're thinking it might be the shaving cream. Can/should we use drano/liquid plumber to clear it? I've heard that they might damage the pipes (pvc) and I obviously don't want to do that. Also, out shower is marble and I'm worried about the chemicals etching the marble. Would that be a problem?
Also -- if it isn't the shaving cream that's doing it, what else could it be?