That makes sense to me too ARJ, thanks. We have the "loop" on our stick house island for the salad sink. I initially thought the plumber just messed up and ran the pipe up the wrong hole and corrected himself. He laughed and told me to stick to being a spectator
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ARJ - In your opinion, is there any reason the vent stack shown in Ozz's picture needs to be at an angle? I would like to modify it enought to maybe add a dishwasher above the HW tank, and that is the only obstruction. Sure don't want to mess up any natural flow of smell to the roof.