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I am finishing my basement bathroom and have run in to a drain spacing issue in my vanity. The PVC coming out of the wall is 20" off the floor. The bottom of the vanity cabinet is 18" off the floor, leaving me about 2" of space between the two. Obviously, I can't have a p-trap that sits below the PVC in the wall given the lack of space in the cabinet.

What are my options in this case? Is it ok to have the p-trap site above where the water will drain in to the wall (would this mean using an s-trap -- which I think is against code)? Or, should I look to extend the PVC in the wall so it's higher up and can accept the p-trap exit at nearly parallel to the floor?

The pictures below are what's inside the wall. The red is my idea of extended the PVC up the wall a bit. The sketch is the s-trap which I think is a no go.

EDIT: 100% sure the S-trap is against code and will create a siphon. Anyone see an issue with extending the pipe in the wall as "illustrated" in my red picture?

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  • Welcome to Stack Exchange. You should take our tour so you know how the site operates with upvotes for helpful answers and checks for accepted answers.
    – HoneyDo
    May 8 '20 at 17:03
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    Typically in these situations you have two options: modify the cabinet to make room for the trap or modify the plumbing height in the wall, careful not to make it to high, figure out the minimum space you need first. Go Pens.
    – Alaska Man
    May 8 '20 at 18:21
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You're right. You don't want an S trap. They are against code. I think your idea to extend the drain up the wall is the right way to go. I'm not aware of any code issues with a short, vertical drain as you're proposing it. This will give you the vertical space you need to install a proper P trap. Make sure that when you install the horizontal piece from the P trap to the drain that you allow for a 1/4" per foot slope in the line.
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  • Thank you for the information. Not excited to cut up my nice, finished drywall.... but at least it will be hidden by the vanity. :)
    – pburgh
    May 8 '20 at 18:54

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