I have been experiencing a moldy odor from the drains in the shower and two sinks recently. The drainpipe in the shower gets covered with a black slime and the sink drain cover has it too. It comes off on the cloth each time I clean the sink. I want to know what I can pour down the pipes to eliminate the slime and maybe it will remove the smell. Could I use bleach on the PVC pipes? My husband removed the traps but they were clear of hair. They were very black and slimy, though. HELP!