So my drain cleared out, believe it or not. (I had a stubborn drain in a cement slab, that I will be using for a shower, see post from yesterday on clogged drain in slab) I can pour water rapidly and freely down the drain. So a new problem... My washing machine is hooked up to the same waste/vent pipe. The machine dump is above that of where my floor drain enters the line. When my machine dumps its water from the cycle it starts to back up in the floor drain. This time it came just about out of the drain, then receeded. My question... what causes this and how do you fix it? Drain woking well now, just need to fix back flow problem. FYI when I am done leveling the floor etc. my drain hole will be a few inches higher than it is now. Thanks again, this forum is great!