Hi all, I think the picture below explains what I want to do best. But basically I want to attach a water butt to the drainpipe. I can't as the drainpipe currently has waste pipes from the upstairs sink and bath going into it, so dirty and soapy water. Is it acceptable to move the two pipes going into the drainpipe overflow over onto the black soil pipe? So nothing comes down the drainpipe but water from the roof.