Shower P-trap 270 loop

[T.J. Fitz-Gerald]

I'm installing a tub/shower and the drain drops to the left side of the HVAC duct and the rest of the bathroom stack (toilet, vanity, vent and main sewer) is on the right side.

There is a 1" subfloor then a 6" space between the joists (where my 2" plumbing can 'comfortably' cross over the top of the HVAC duct). I can't take an immediate turn to the right due to the HVAC duct but I can, if it will work, loop the P-trap to the left with a 270 degree loop ending with the discharge going right. I can even squeeze in a 1½" wye for venting if it's necessary (which I'm pretty sure would be a good idea too).

In the pictures attached to this post, I'm holding some silver ducting where the actual HVAC duct is in relation to the drain, there is a tape measure and the tip is at the bottom of the joists, there is green painters tape wrapped around the drain showing the portion of the drain that is above the subfloor.

 

[Terry]

You are allowed to swivel the trap.
The trap gets vented within five feet.

 

[Sponsor]

 

[T.J. Fitz-Gerald]

Thank you for your extremely rapid and helpful reply. I will post a completed picture when the installation is complete.

 

[Reach4]

Tubs are often wet vented. See https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf page 12.

 

[T.J. Fitz-Gerald]

Here's the current status of the bathroom replumbing project:

Drain & Vent System:
Starting from left there is a 1½" vertical pipe to the left of the lavatory drain for an Air Admittance Valve, the 1½" extends through the notched 2x4 studs (non load bearing wall and black nylon straps will be replaced with metal stud protectors) and extends past the tub/shower valves where it connects to a wye T where a second Air Admittance Valve is connected and in place in the photo. It then goes down through the floor where it will tie into the tub/shower 2" drain and to the 3" main sewer stack which is nearly centered in the picture (to the left of the toilet fresh water line shown). There is a 3" wet vent from the 3" stack feeding to a 2" which vents to the outside (there is a point where it gets reduced to 1½" for about 3" as it passes through the floor and wall sill before reconnecting to a 2" pipe that vents through the roof).

Supply Lines:
Cold water line is the lowest and consists of ¾" cpvc until the end where it's reduced to ½". Hot water line is also cpvc and is a bit higher (11" off the floor) and comes through the floor as ¾" but is reduced to ½" before passing through the first stud. Supply lines are provided and in place for a lavatory, toilet & tub/shower wall.

I'm about to test fit the tub back in place and hope I don't have to redo any of the far right drain drop (it's tight).

 

[T.J. Fitz-Gerald]

Tubs are often wet vented. See https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf page 12.

Aren't many tubs effectively vented through the tub overflow as well?

BTW, this tub does not have an overflow and I've decided not to install one at this point.

 

[Reach4]

Aren't many tubs effectively vented through the tub overflow as well?

Plumbing vent is on the downstream side of a trap. Overflow is on the upstream side of a trap. The trap prevents sewer smells and gases from entering the room.

 

[wwhitney]

View attachment 67108
Starting from left there is a 1½" vertical pipe to the left of the lavatory drain for an Air Admittance Valve

Look like you used a sanitary tee for the lavatory drain inlet. That needs to be a combo, the sanitary tee can't be used in drains in the orientation shown.

the 1½" extends through the notched 2x4 studs (non load bearing wall and black nylon straps will be replaced with metal stud protectors)

On the axis perpendicular to the wall, what is the offset between the front edge of the pipe and the front face of the studs? I think a better repair than just a nail plate would be a good idea. If any of those studs are going to be supporting a tiled area, it's arguably necessary.

and extends past the tub/shower valves where it connects to a wye T where a second Air Admittance Valve is connected and in place in the photo.

Why two AAVs? I don't see what the second one gains you.

Your description of the drain lines below the floor was hard to follow, so if you have any questions about that, a diagram would be helpful.

Cheers, Wayne

 

[T.J. Fitz-Gerald]

These are the images of how I ended up "snaking" the drain pipes under the subfloor, over the HVAC duct and into the toilet stack. A bit unconventional, I total admit that, but I was working alone in a tight and uncomfortable space. I used some nylon straps screwed into the subfloor merely to hold the PVC drain pipes in place while I was attaching the other ends into the main stack. The bathtub dumps directly into the main stack and does not have an independent vent but there is a main vent directly off the stack and an AAV off the sink drain and both of those vents are within 5' of the tub drain (measured by the pipe not line if sight). There is also a second AAV near the sink too (I'm a pilot and we welcome redundancy). The "P-trap" is more of an "O-trap" with it's contortions. I had thought of joining the sink drain directly into the bathtub drain but frustrations won and I made the "executive decision" to rely on the proximity of two separate vents instead of tying the two drains together.

The bathtub drain goes straight into the stack (after going through the P-trap), the sink drain travels 4 1/2' horizontally then joins an AAV, drops 18" with a slight 22 1/2° jog to avoid joists then comes 90° back to the main stack where I had to add an extended double 90° sweeping bend to drop into the lower inlet into the sewer stack. Pictures will hopefully clarify my description.

Thank you for the alert on the sanity-T comment at the sink. I haven't changed that piece yet so I have to ask how big a deal is a sanitary T instead of combo or Wye coming off a sink where no solids are discharged keeping in mind I'm using 2 AAVs on that line too? I'm heavily leaning towards replacing it but just asking because that's going to make drywalling a bit more difficult but not impossible.