Several days ago, an overflow pipe in our basement (originally there, I believe, to handle a washer/dryer connection, but now unused) started to overflow and release water with food particles and other sediment onto our basement floor. Then last night, our kitchen sink (which is above the basement and apparently 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, when checking the overflow pipe in the basement this morning I noticed that this pipe is still overflowing with water (although not steadily). The water coming from this pipe also appeared to contain some of the drano product in it.

Is this a clog that can still be cleared by further applications of foaming drain cleaning products, or will it need to be snaked out? Or will something else need to be done? Any suggestions you could offer would be much appreciated. Thanks!