Plumbing for full bath in 2x6 joist bay with homemade p trap

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mgmunson

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I've searched every discussion I could find on this topic, and the general consensus is raise the floor or drop the ceiling. My situation may be the exception (yea, everybody hopes that).

I'm building a timber frame home with a bathroom on the second floor. Finish ceiling (pine 1x6 t&g) sits on structural timbers. 2x6 floor built out on top of the pine to chase electric, hvac, and plumbing. I have to cross 3 joist bays to get to lavatory/wet vent/main drop. That's what stands in the way of most 2x6 floor plumbing situations, you can't get the required drop and maintain structural integrity of the joists if you have to cross. I'm crossing the joists directly above and parallel to a structural timber so I maintain bearing onto the timber regardless of where I notch the joists vertically (it's a 2" hole above a 6" timber, I leave 1 3/4" bearing on each side).

Where I was having trouble was fitting the p trap under the subfloor. What I did was make my own p trap using 1 1/2" 90s offset at a 45, then another 45 for the riser. I maintains over 2" of water in the trap and, I believe, satisfies the definition of a p trap.

Am I barking up the wrong tree, or do you agree this should satisfy code?

Thanks!

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GReynolds929

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Won't satisfy code in my area. It lacks self scouring design. 3 90's and a 45 or two would work. 2x6 floor joists seem small to me. What's the support like?
 

mgmunson

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Hmm.. I would think it scours the same as any self-assembled p trap. What would you say prevents this from self-scouring? That's exactly what it is, 3-90s and a 45. I'm going to pitch my case to the inspector, as he's really the final say. I'm just testing my argument here before weighing any other options.

My support is 6x10 beams 3ft on center perpendicular to the 2x6 joist chases. The plumbing run across joists is directly over one of the beams, leaving the 2x6 directly bearing on the 6x10 (pic 4).
 

wwhitney

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Use a standard 1-1/2" solvent-weld p-trap. The c-t-c from the bottom of the u-bend to the outlet is 3.86". A 1-1/2" pipe is 1.91" is OD. That makes 5.77" in overall height, plus the extra height for the hub, maybe 0.25"?

At 6" total height, you could relieve the ceiling below and/or the subfloor above to get your extra 1/2" of clearance. E.g. use a large forstner bit to drill a 3/8" deep hole into the backside of your pine 1x6 t&g for the bottom of the u-bend.

Cheers, Wayne
 

Jeff H Young

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sure standard trap you should be able to sneak in. a standard tub should hook up with a solvent glue type waste and overflow .
 

Tuttles Revenge

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I've had to sneak in traps like that. But the last 45 is pointless. It just requires the 3.
 
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