Overflow from W/D drain in basement
Several days ago, a pipe that was used to drain a washer/dryer in our basement (but is no longer used) started to overflow and release water with food particles and other sediment onto our basement floor. Shortly afterwards, our kitchen sink (which is above the basement and is tapped into this line), backed up completely on both sides (it contains a garbage disposal on the left side and a regular drain on the right). This also contained quite a bit of food sediment and sludge.
I applied drano gel to both sides of the sink, and after about an hour, they did clear. However, the pipe in the basement continues to overflow whenever the kitchen sink is used.
Also--and perhaps most importantly-- none of our other bathroom sinks, toilets, shower drains, and the washer-dryer hookup that we use now on another floor are affected in any way by this (no backups or overflows, etc. in these areas). The floor drain in our basement is also draining fine, too.
My questions are:
1. Is this a clog somewhere in the line to/from the kitchen sink and old w/d drain?
2. Should I continue to try to clear this by further applications of either a gel or foaming drain cleaning product, and if so, should I try to apply it through the old w/d drain pipe?
Or, will the line have to be snaked out or will something else need to be done?
Any suggestions you could offer would be much appreciated. Thanks!