Garbage Disposal - Water Shoots Up Non-Disposal Side

Question

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?

Answer 1

Replace that 4 way junction with two wyes offset from each other (you might drop the disposal trap a few inches to achieve this) and extend the aav arm as high as possible.

The pressure from the disposal may be forcing the aav shut, and between the poor configuration of the hub and the resultant lack of venting the opposite sink is the path of least resistance.

Yes you will have to chop that monster out. If you can't configure two offset wyes at least get a double wye hub and raise the aav.

Answer 2

Get rid of that double trap setup and that PVC tee monster. Configure a single p-trap to a waste ell on the vertical waste pipe coming out of the floor. A baffle tee goes to the top of the trap with the garbage disposer dumping into the top of it and the other sink plumbed into the side port of the baffle tee. Do not use any of that flexible accordion type fles anywhere in the system.

Answer 3

Et voila. This is what you should aim for, but where I drew the red circle you'll replace the wall tube with another tee that goes up to the vent and down to the drain. Turn the disposal around as pictured here. Use drain tube just as pictured here rather than gluing anything then it's easy to align everything and you don't need a cleanout.

Answer 4

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.

Answer 5

I am not recommending this but only because it reminds me of Terry Gilliam's movie Brazil I'm adding this $28 all-in-one monstrosity solution. You would add an AAV instead of a wall flange.

Answer 6

Use disposal inlet and drain sink into disposal.

I lived in a house where the sink drained into the disposal. It looks like you drain the dishwasher into the disposal already because that port is in use by some flexible pipe. That intake could do double duty. You would need some sort of T adaptor.

In the house where I was the sink would back up if the disposal needed to be run, just as the disposal side does if the disposal needs to be run. There is an easy fix for that: run it.

You could keep the much here-hated on T outlet you have now (which has the benefit of already being there) and just cap the sink side. Then use the also hated on flexible stuff to make a drain line similar to that used for the dishwasher.