plan for vertical wet venting the tub via the lav in the master bath

[NSB000]

The lavatory, WC and bathtub in the master bath are all independently dry vented (original construction 1965).

I want to wet vent the bathtub via the lav so that I can eliminate the tub's original drain and vent pipes (that gives me a pipe-free wall and would allow me to make unrelated remodeling changes). This wet vent plan appears to be doable after referencing Minnesota plumbing code (UPC) and reviewing related threads here.

I created an isometric drawing for the addition of the tub wet vent in the master bath. If a different depiction would work better, I can do that.

I think I can summarize the changes here:
- the vertical pipe for the lav (drain & vent) is currently 1-1/4"; all of the 1-1/4" will be removed and replaced with larger diameter pipe
- the tub trap arm is currently about 1 ft long using 1-1/2" pipe; the new tub trap arm will be about 52" long using 2" pipe

I have done my best to ensure the changes comply with the UPC for Minnesota.

I hope I didn't neglect or overlook anything in my plan. Any feedback to get the plan right is welcome.

changes to be made:
- increase pipe diameter of vertical dry vent section above lav santee from 1-1/4" to 1-1/2" to accommodate 3 DFU: lav (1 DFU) + tub (2 DFU) (table 703.2)
- increase pipe diameter of vertical wet vent section below lav santee (and above tub santee) from 1-1/4" to 2" (section 908.1 Size (for wet vent))
- insert tub santee (2" x 2" x 2") below lav santee
- increase pipe diameter of vertical drain pipe below tub santee from 1-1/4" to 2" to accommodate 3 DFU: lav (1 DFU) + tub (2 DFU)) (table 703.2)
- change direction of tub's trap arm 180 degrees, away from the wall and toward the lav drain
- change tub trap arm pipe diameter from 1-1/2" to 2" since the distance from the redirected tub trap weir to the lav drain pipe will be 4'4" (52"; greater than 42" and less than 60"), [table 1002.2]; 2" trap arm pitched 1/4" per foot
- change tub trap ID from 1-1/2" to 2" [section 1003.3]
- replace original lav santee with 1-1/4" x 1-1/2" x 2"
- cap off abandoned tub santee (original drain & vent pipes to be removed)

 

[wwhitney]

Looks good.

If you are replacing the lav san-tee, you might use a 2x1-1/2x1-1/2. Then at the wall you can use a 1-1/2" or 1-1/4" trap adapter as desired.

Note that the trub trap arm may fall at most 2" (one trap diameter). 52"/48" = 1"+, so it will work if you stick with 1/4" per foot slope you indicate. But if you exceed that slope, you need to stay under 1/2" per foot.

Cheers, Wayne

 

[Sponsor]

 

[NSB000]

Thanks for the input. Great recommendations. I will replace the lav santee as you suggest with 1-1/2" at the trap arm inlet. And I will ensure the drop of the tub trap arm does not exceed 2".

 

[Jeff H Young]

yea no one uses 1 1/4 on homes unless there is some reason like fancy trim . except on RV or mobile homes