Hello, I was wondering if it was safe to pour bleach in a cast iron basement floor drain? I have a floor drain in my basement and when I run my washer it raises up about 2 or 3", "still about 8 inches from the top of the drain" and kinda blurps while the laundry sink is draining, as soon as it is done draining though it goes back to normal. I am sure it is a cast iron drain because that is what is is comming up to my bathroom. The basement floor drain is concrete untill it gets to the trap at the bottom. My long time plumber friend is very busy on a job and since he cant get over to snake it for awhile he told me to pour a gallon of bleach in it and let it sit overnight then flush it out. my only concern is will letting it sit that long damage metal drain pipe? right now it has not even came close to the top of the drain but it has never did the blurping sound before so I figured I would try the bleach. any help I truly appreciate. Thanks.