I have a dishwasher upstairs and when it drains I frequently (most of the time) end up with waste in my downstairs shower. It does not happen from ordinary use of the sink and was made better when I routed the dishwasher from it's own drain in to the garbage disposal under the sink.

I believe the issue is the "T" at the bottom in the basement floor where the kitchen drain/shower/exit to septic meet (interestingly, the washing machine drain seems to meet there also but does not cause this problem), but I'm not prepared to tear up all the cement floor to replace that somehow.

Can I simply slow down the drain from the kitchen? Put an additional trap along the way, or perhaps a box (like a catch basin)?

Ideas?

Traps and 'boxes' would probably not help the situation, but would create other problems of their own. Draining into the disposer should not have made any difference because it is an "open" drain just like a dedicated one for the DW would have been. An air gap MAY change the flow enough to stop the condition, but you would not know until you tried it.

I'm not sure what you mean by an "air gap" though....can you please explain a bit more? (I'm willing to try it in the hopes it will help).

I'm guessing that the pump in the dishwasher is just throwing the refuse down the drain "too fast" so it ends up backing up in the shower drain. I don't remember this problem cropping up when the place was new (1960's) so I'm wondering if there are other contributing factors; like stronger pumps nowadays or perhaps build up in the drain.

I am having the drain snaked professionally next week to see if that helps.



Edited 3 times.

i'm guessing a drain cleaning will solve the problem.