Why does my upstairs sink and wahser machine flood the floor drain in the basement? Every time I use the washer machine or wash the dishes in the upstairs sink it flood the floor drain in the basement, and if I am washing clothes I have to stop the water from draining into the washer sink in the basement by openeing the washe door and letting the water run out so the water doesn't flood, it is ridicoulous and takes for ever to wash my clothes, and now it has got so bad that I am washing dishes in the tub because the bathroom tub and toilet and sinks doesn't flood the basement at all, what do you think the problem is?

I'm not a plumber, but this really sounds like it is probably related to venting. I would suggest you either don't have enough vents in your plumbing system, or the ones you do have are not in the right spot. As I said, I'm not a plumber but that's the first thing I would look at.

Sounds like you have a partial clog in your main drainage line, if you are handy you can rent a plumbers snake from home depot, but be careful that tool is a beast of a machine and can/will hurt you bad if not used properly, or you can call a plumber to run a snake to clear the stoppage. Hope this helps.

Do you know if your bath drainage system enters the main in a different area than the washer? i.e. front of your house - back of the house.