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Kitchen sink - soap backs up

Rebuild of the kitchen sink plumbing was required when we decided to remove our garbage disposal. Replaced all the sch 40 PVC. I brought both sink drains to a T then down to a P trap and out the cabnet to where grey water normally goes. Before replacing we did not have problems with soap backing up in the unused sink. We use the same amount to wash hands and dishes with. Any ideas or tricks - our friends at home depot and lowes are clueless as is the facilities plumber at my work. Thanks.

Blue RidgeParkway
Re: Kitchen sink - soap backs up

First if your new arrangement isn't properly both trapped and vented you're going to have problems.

Second, and most important - if you used a venting tee or other incorrect, improper fitting or you installed it in an incorrect orientation you'll have the problem you are describing.

There are fittings that may "look" like a tee from the outside but are not a vent tee, they are sanitary fittings (which provide a slight offset for the horizontal connection(s) so pitch is maintained and they contain a baffle which prevents flow of liquid or air to the other sink bowl. there are different fittings depending on if the orientation is vertical for one bowl and the second bowl is draining from a horizontal arm, or if both bowls are draining from horizontal arms and the fitting transitions to a vertical direction (then down to the trap).

If you snap a photo from under the sink cabinet I'll link you to a drawing or diagram of the fitting.

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