Dual sink disposal possibly incorrectly installed

Hi guys,
buying this new house has brought a whole host of new problems for me.

I found this forum after googling the subject and seeing a previous related post 'https://terrylove.com/forums/showthread.php?1736-install-garbage-disposal-in-double-sink'

I have the badger model 100-1 disposal, with a dual sink setup, with the sink and disposal on the right, and the 'other' sink on the left, along with a dishwasher.


and yes, Ive seen the reviews on this thing, I know, its not a 'great' disposal, but the entire kitchen was remodeled before I bought the place, so I figured I would keep this until it broke.

however, the issue I'm having, as shown in the photo, I dont think the pipes are setup correctly, when I use the disposal, it pretty much just sucks the water out from the disposal-attached sink and spits it out into the other sink.

I dont believe its clogged as it has literally never been used before.
?
here is a photo of the setup, I was thinking this is missing an air-vent, but maybe I am wrong entirely



thanks in advance!

There is no visible vent. Do you see one outside, on the roof, in the area of the kitchen?

Disassemble the left sink horizontal arm and the end outlet tee (the white piece below the black disposer discharge) - clean them. The end outlet tee should have a divider inside, to separate the water coming from the disposer and from the left sink. If not, replace it. I would clean the trap as well.

Assemble in reverse order. Check for operation and for leaks.

Other than that, this arrangement setup that you have should be OK, except that I like to have the disposer on the left sink.

You have an S-trap, even if there is a vent somewhere else downstream. To be a P-trap, you need a vent coming off the drain line before the trap arm turns down. If your area allows an AAV, you could install one. Essentially, you'd cut off that curved piece from the outlet of the trap, add in a Y, adapt the outlet of the trap into that Y, and on the upper (straight up) section of the Y, go up as high as you can, then install the AAV. You need to be able to unscrew the AAV eventually, since they do fail, but it needs to be as high up in the cabinet as you can get it.

However, as a practical matter, the lack of a vent is NOT causing the backup, UNLESS you also have a blockage somewhere and if so an AAV would not change the situation.

I'm not a plumber but definitely there is no vent. You say, "a new house" but is sounds like it is not new construction and someone did a remodel of the kitchen. The remodel probably moved the sink to a new location. A city inspector(for a permit) or a house inspector (for a home purchase) should have found this. Why the water is coming out of the the other sink is as the water from the disposal side is going down the pipe and it is trying to push the air down, but the air in the pipe wants to go up and it brings some of the water up with it. The side pipe to the the other sink is of the least resistance because there is water in the disposal pipe. To prove this get a funnel and place it in the neck of a bottle and be sure that the neck of the funnel is tight around the bottle neck. Now pour water into the funnel and you'll see what the happens.

The picture shows a P trap parts but it is in an S configuration. The experts have not yet commented on this but is maybe a concern. I do know that in some areas of the US that S traps are not allowed because with the rush of water down the pipe can still suck water out of the trap. I assume the pipe goes down into a basement or crawl space. I would relocate the main drain and install an AAV. If you can I would place the disposal on the left bowl and tee into the other sink drain.

Perhaps some of the plumbers on this site would comment on this setup.

A plumber would have thrown away the 90 bend that came with the disposer and used a disposer kit. That would be a straight flanged pipe from the disposer to the baffle tee.
The dishwasher would install to the disposer with an air gap, or at the least, routed as high as possible before connecting to a drain.
As shown by the handyman's picture, the dishwasher is below the trap of the kitchen sink as a wet vent. Not legal everywhere.

The drawing I post, could have used and AAV instead of the vent through the roof where allowed.

Terry is right, the picture I attached I was looking at the sink/disposal connection only. I always connect the dishwasher to the disposal and loop the drain line from the dishwasher through a hole at the top of the end of the cabinet. One advantage is other than making a questionable wet vent connection is the disposal gets cleaned every time the dishwasher drains. Without hot water running through it, a disposer can get pretty bad in the odor department.