A plumbing book I have says a kitchen sink sewage inlet should be at 16" above floor. I would like to set it a little lower (e.g. 12") in order to make more room around water stubouts for plumbing as well as provide more vertical clearance for a deep sink with a garbage disposal.

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Are there any disadvantage to setting it lower?

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    Off topic: Your tee is oriented backward. (Maybe you're just mocking it up.) – isherwood Feb 15 '16 at 18:39
  • Yes, I was just trying it out – amphibient Feb 15 '16 at 18:53
  • If you live in a place with codes, call your code enforcement office. They'll know what codes might be in effect in your area. Code vary from place to place and don't always make sense so although something might work just fine, it still might not be legal in a given area. – Sean Dec 22 '16 at 15:08

No problem and you can go very much lower. It's done everyday for garbage disposals attached to deep sinks and even laundry tubs. I've even seen traps resting on the room's floor with the cabinet bottom greatly notched out for servicing and replacement (plain ugly)...the sink drained exactly like it should and I had no problems washing my tools and buckets.

Additionally, the sink's tailpiece that goes into the trap assembly can be up to a maximum of 24" long. Initially, I couldn't find a public Code Reference, but there is 1 here https://www.law.cornell.edu/cfr/text/24/3280.606 to substantiate this very rarely seen setup.

Your situation seems to be a basement or on-grade slab. Though, if there were a readily accessible crawlspace or garage below the deep sink and its garbage disposal, an up-to 24" tailpiece could place the trap in those areas and not in the sink's cabinet or room at all. In operation and regulation, there's little difference between a sink, shower or laundry standpipe trap.

Side with immediate and easy access in all cases. Not seeing a P-trap in the sink's cabinet will have most Home Inspectors and Newbie Building Code Inspectors hyperventilating and clutching for their red pen. Although, these idiots will still happily approve all illegal horizontal drywall installations, amazingly.

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  • I agree I have seen them many times within a few inches of the bottom of the cabinet. I believe the reason for having them higher is to provide storage and working space. – Ed Beal May 3 '17 at 16:02
  • Yeah, I'd agree with having a few inches of clearance, so just the trap can be dropped for cleaning, replacement or ring retrieval. Only once did I see the sink's tailpiece as the only thing in the cabinet and boy was that a clean, dry and maximum storage cabinet...quite appealing in the right situation. Very much unlike this horrendous hilarity of idiocy by 2 "Master" plumbers youtube.com/watch?v=HkFTnnFbh-s at least the 1st one did it to put in a cleanout, though shamefully pointless. – Iggy May 4 '17 at 12:07

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