Understand this is asked often. Each case is different though and have not found someone with my plumbing configuration (see pictures).
So when we turn on garbage disposal we get water shooting up non-disposal side just about every time. I am almost sure it is not a clogging issue. As a test I filled non-disposal side sink entirely with water and pulled plug, observe no water backing into garbage disposal or garbage disposal side sink (i.e. it is going down drain quickly). I am convinced this is one of those "garbage disposal shoots with great velocity, takes path of least resistance, goes up non-disposal drain".
I have attached pictures of my plumbing.
Based on all I have read it seems the disposal drain needs to tie in using a T-Baffle to force the waste to go down and not shoot across the 4 way connector. If you look closely a lot of the pieces are glued. I don't think I can get that 4 way connector out without cutting.
What would be the best solution? Some sort of check value in the non-disposal line?
Update – Added additional sketches and a picture of our home exterior to illustrate it would be difficult to have an exterior vent.
Jimmy's Solution. Question – where would AAV go?
Exterior – I have included this picture to illustrate how difficult it would be to have exterior vent. The top of the 2nd roof is rubber/flat. The vent stack for bathrooms is far removed.
Double Wye – Could I simply replace the 4way connector with this?
Best Answer
Apologies for the mickey mouse sketches. There are lots of CAD gurus here who would rightly shame me for this .... but anyway .... top is what I believe @JimmyFix-it intends. I think it's the better suggestion. Bottom is roughly what I've suggested. Shaded in the top diagram, two baffle tees, and in the bottom, two wyes offset vertically. Yes there's an AAV either way. Try to shove it up between or behind the sinks as shown.
Either way you should add a cleanout, which I forgot to draw. If you use compression drain fittings for the baffle tees you don't need to add one, but if it's all glued up you can add a straight compression fitting between the AAV and the tee it joins.