Home Forums Hunting & Shooting Hunter's Campfire Plumbing question

Hoping someone can help me with this plumbing issue. Plumbing in a new vanity in the bathroom. The vanity has a built in shelf that I would like to utilize for space. If I plumb it as a straight shot out of the p trap to the wall the trap/pipe is directly in the center of the shelf and about 1/2” above the shelf taking up a lot of the space.
Can I plumb it using a 45 out of the wall to gain some height/clearance from the shelf. I’ve included a “bad” sketch of what I hope to use. Using 1 1/2” abs for all pipes also.
Any insight greatly appreciated. Thank you!

That looks awful close to becoming an (S) trap, which are no longer code.

PM Happy Camper. Ain't nuttin' he hasn't done,

no reason it can't drop after the trap.
its gonna drop somewhere in the wall..
the lowside of your trap willfunction like a low dam..
as long as long hairs dont hang up and create a streaming clog it seems workable..
but I am no plumber....

That is a 3/4 S Trap. It may siphon all the water out of the trap allowing sewer gas to come back into the room as well as flies and vermin. Illegal traps below.

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This is a proper installation

I sent that sketch to my plumber, he said NOPE.

Thanks guys.
What if after the trap I went straight pipe for let’s say 3-4” then 45 down toward the wall?

Is it code? No.

Will it work? Yes.

Will it be a problem? Mostly only if you fill sink full of water prior to dumping it to drain and siphoning trap dry.

Workaround? Run enough water to fill the trap after emptying the sink.

Any houses plumbed this way currently? Many older houses have never been changed to P-trap.

hanco,
OP's sketch looks like the turn to 45 is more than a full pipe diameter above the top of the bottom turn.
does that make a difference?
your 3/4-S looks to be less than a full pipe diameter above.

Doesn’t matter, will still siphon water out if a full bowl of water dumped down drain.

How long can you make the waste arm extension before hitting the back of the vanity?

If 3.75” or so, and the drain line is vented inside the wall, you shouldn’t have a problem with it flushing itself dry.

A terrible installation example, lavatory looks OK except it’s undersized and fittings are not long sweep fittings. Toilet and shower are flat vented, didn’t use wyes and 1/8 bends at changes of direction.

Would it drain ? Yep. You might have hell getting a sewer cable down the line.

Thanks guys. I’ve attached another bad sketch with the waste arm from the p trap. I think I can make that 4-6” before the 45 to the wall. Would this setup work? Could I use 90s instead of the 45?
It is vented inside the wall straight up to the roof.

Keep life simple, get rid of the shelf......

Or, I doubt your first drawing has the ability to drain the trap by suction,

You wanna go full blown Alabama on it, go for it.

Thank you. Sometimes it’s easy to over complicate things. I can make it work with the shelf but I’d like it to be useable space as the bathroom is pretty small and storage space would be nice.

Put a shallow wall cabinet over the toilet. Easy storage option.

That was the plan also. Thank you.

Then fish stuff out of the spring.
Unless everyone in the home keeps the lid closed.
All the time! Absolutely every moment a butt isn't covering it.

Need to keep the PTrap or Weir below the connection level of the vent in the wall.

Still a S trap, 90’s or 45’s, doubt if it would siphon unless bowl full, then the water cut loose, probably enough residual water in bowl to fill trap anyway. Try it, you can always change it.