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Why does my food disposal send water to the other sink bowl?

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LilyT

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Hi there,

I have a double bowl kitchen sink, see picture below. I use OXO sink strainer in both bowls to catch food peels and dump them to trash can every day, I do not wash them down the drain. However, once in a while when I notice the water (standing about 2"~3" deep in the left bowl) drains slow, I reach for the food disposal switch, then I would see water coming out from the other bowl's sink hole. It seems the food disposal shoots out water too fast in great amount & force, more than the downward pipe can handle.
KitchenSinkQ.jpg LongTeeWye.jpg DWTailPiece.jpg
I have several questions here:
1. Is it common for food disposal to send water to the other bowl?
2. Am I using the food disposal wrong, should I not to use the food disposal when there is standing water?
3. If I replace the tee fitting at location 4 with the long tee wye fitting, would it make the situation better?
4. My dishwasher drain hose connects to the food disposal (at location 3) in a high loop. My dishwasher has fine mesh metal filter at the bottom. Most modern dishwashers come with those or are equipped with their own food chopper blades, they do not need traditional disposal to disintegrate the food. Hence, I think the dishwasher's drain hose do not need to connect to the traditional disposal at all. In that case, what part to buy to plug the hole on the disposal? Can I replace the pipe at location 5 with the dishwasher branch tailpiece? That section is very short. The tailpiece might be too long to fit in there.
5. About the plug at location 1 and sewer vent at location 2, it's not common to see them under the kitchen sink. I'm not the first owner of the house. I wonder if they were installed/added later to improve the drain performance at this specific location. Do you know why they appear here?

Sorry to load this post with so many questions. Please shed some light if you can. Thanks a lot!
 

breplum

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1.The slip joint tee (4) would typically be a "baffle tee" in that it has an internal casting thwart to help direct flow down instead of across and up.
those plastic baffle tees don't have the best flow characteristics and can clog readily if not enough water is used in relation to solids (not an issue bc you state you use the excellent OXO Good Grips sink strainers.
2. Most garbage disposal kits offer two outlet pieces as options. One like you have and the other a 90 degree elbow which directs flow down.
It looks like you have the room to use one of those elbows and that could help. We always try to use the 90 b/c the straight does often cause a complaint like yours.
If you did find and use a 90, you would need to purchase a "continuous waste end outlet" kit (plastic is ok, but the baffle tee from a brass/chrome metal kit has MUCH better flow characteristics).
On the other hand, your in the wall drainage could be less than wonderful and causing some resistance, even though it looks like the drain in the wall (based on the cleanout (1)) looks to be 2" ABS which is perfect.
The AAV (2) is pretty ok. They are only req. to be 6" above the trap so you are good there.
 

LilyT

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Thank you, breplum!
You are suggesting to connect as in the following picture. I have 2" vertical space to work with, not sure if it's enough. Why not just use a long tee wye fitting at location 4, which has less pieces involved?
elbow.jpg
 

LilyT

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I saw some articles talking about proper usage of sanitary tee vs wye, like in this picture. Am I restricting the vent air if wye is used?
TeeWye.JPG
 

breplum

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I think that picture may be relevant.
But, on a sink, where flow is fairly low, wouldn't be much of an issue.
On the other hand, nobody I've ever known has had to bother with odd fittings bc normal fittings work fine. Just my experience with 46 years plumbing.
 

TomFOhio

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If your running water in the disposal and it backs up in the other sink your drain line going into the wall
is plugged and needs opened up.
 

LilyT

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If your running water in the disposal and it backs up in the other sink your drain line going into the wall
is plugged and needs opened up.
The water just goes to the other sink momentarily for 1~2 seconds, then drains away.
 

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