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I have drain that is a bit too low so I may have to cut lower drawer on my vanity (see my other question).I want to avoid that. There is 4" clearance behind the drawer. After some research it appears that the only legal way to install trap is to keep its arm on the same level as drain entry. So I can't raise the entire trap. So I am thinking of making 90 or 45 degree elbow to route tailpiece to the trap behind the drawer. I can see some ADA tailpieces done that way but I may need to customize some more. Apparently the height of the entire construction can't be over 24", which is ok.

Is there anything else in code that can prevent doing it legally? Will this construction pass inspection? Note that it's California plumbing code which is UPC based.

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up vote 1 down vote accepted

It's a grey area. Nothing explicitly says you can't, nor explicitly that you can. An inspector could reject it based solely on it preventing the fixture from "draining rapidly". I see your proposal as OK, it's no different than adjacent basins sharing a single trap. As long as the horizontal offset is less than 30" and there is not more than 90 deg horizontal change of direction.

Under such circumstances, no one can predict the result of an individual inspection. You can either enquire in advance, or just do it, having a more conventional plan B should there be any objection.

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