What causes water in washing machine line to come back out drain. Have used everything recommended and also dug up lines and found nothing.

Hi Ejgrubbs:

There are only two things that cause a drain to back up... a clogged drain or a clogged vent... ;)

By your description I would guess that you haven't snaked the drain far enough or you went to far and actually passed the blockage. I would suggest that you start by snaking the drain line if possible, but first check the washer standpipe and the washer PTRAP to be sure these are not the issue. After that, you need to snake the drain line up to where it connects into other, larger plumbing pipes.

First, however, check that the VENT to the washing machine isn't clogged.

Now, what do you mean that you "dug up lines"? Did you dig up the pipe and replace it? When you had it dug up did you confirm that water is getting to the spot you dug up?

Back to you...

MARK