Galvanized steel to PVC in bathroom: plumbing vent + tub drain

[Dan]

hoping to get some feedback on my work. i should have done this before doing the work but here we are. i'm hoping not to rip it all out and do it again but there's that possibility. i would rather do it again now than after a failed inspection. i am most confused about the sanitary tee for the tub/shower vent but someone at a big box store said it was fine (better or worse than someone on the internet?).

plumbing vent for the shower+tub combo

problem
- shower/tub combo plumbing vent non-right-angle going across ceiling joists and in the way of other work (e.g. lights, skylight, etc)

work
- replaced vertical galvanized steel with 1.5" pvc
- re-route horizontal plumbing vent with 2 right angles

photos: before (i.e. diagonal galvanized steel)
https://i.imgur.com/rcDSgSB.jpg

photos: after (i.e. pvc replacement)
https://i.imgur.com/mG5w0wy.jpg
https://i.imgur.com/r791nYI.jpg
https://i.imgur.com/ihsiiFn.jpg
https://i.imgur.com/6PQG7uh.jpg


drain for bathtub+shower vent connection

problem
- removed galvanized steel tub/shower combo plumbing vent

work
- dropped in-place of galvanized 'tee' with pvc
- no-hub coupling to go from galvanized steel to PVC
- 2"x2"x1.5" PVC sanitary tee (found here)
- replaced adjustable p-trap for bathtub (1.5" tubular)

photos

https://i.imgur.com/NKuHiUQ.jpg

 

[wwhitney]

So are you under the IPC or the UPC? The UPC has language that prohibits a sanitary tee on its back for the vent take off, and requires a combo. That language is not in the IPC, so I believe it is allowed.

Also, I believe that the trap and trap arm are supposed to be the same size. So with a 1-1/2" trap, you'd stay at 1-1/2" until the vent take-off, i.e. a 2" x 1-1/2" x 1-/2" san-tee would have been better. Not sure what the technical reason for this requirement is.

Cheers, Wayne

 

[Sponsor]

 

[Terry H]

IPC allows San tee on its back for venting as far as I’ve ever been taught. Inspectors let it fly here.

 

[Dan]

So are you under the IPC or the UPC? The UPC has language that prohibits a sanitary tee on its back for the vent take off, and requires a combo. That language is not in the IPC, so I believe it is allowed.

Also, I believe that the trap and trap arm are supposed to be the same size. So with a 1-1/2" trap, you'd stay at 1-1/2" until the vent take-off, i.e. a 2" x 1-1/2" x 1-/2" san-tee would have been better. Not sure what the technical reason for this requirement is.

Cheers, Wayne

thanks. UPC. so gotta cut that out tomorrow. all the references for the sanitary-tee laying on its 'back' was for water/solid draining rather than vent so I thought it was ok for a vent.

I'm confused about your reference to a 'combo'. is that a 'long sweep' 90-degree as seen here (but 2" x 1.5" x 1.5")?

if this is the product, i'm going to have to make my own with my own fittings, i can't find a 2" x 1.5" x 1.5" combo in stores. could I use a wye + 1.5" straight pvc + 1.5" 45-degree pvc eblow? i'm not even sure i can find a wye that is 2" x 1.5" x 1.5" (quick online search)

 

[Terry H]

A combo is a wye that has a 45 also. It’s like a wye with a sweep on the arm of the wye. And get a 2x1-1/2 bushing to glue in the hub ends to make it how you need it.

 

[Dan]

A combo is a wye that has a 45 also. It’s like a wye with a sweep on the arm of the wye. And get a 2x1-1/2 bushing to glue in the hub ends to make it how you need it.

got it, thanks.

well issue is i can't find a wye or a 'combo' in 2" x 1.5" x 1.5" (needing to take care of that p-trap going into a 1.5" rather than a 'reducer' 2"-to-1.5"

to clarify: i cannot use the 2" to 1.5" pvc reducer to connect to the p-trap 'arm'? if that is correct then i'll have to order a 2"x1.5"x1.5" combo online and wait for it to come. (it would be REALLY nice if i could use a 2" x 1.5" x 2" wye + 45-degree stree elbow. maybe saying it enough times makes it up-to-code?)

 

[Terry H]

Oh I see what he was saying now. Yea I don’t see why that would be a problem. A brushing would reduce at the fitting but you just did it a couple inches out. Surely they’ll let that slide.

Look for a bushing they fit inside of the fitting and reduce there since you are cutting it out anyway.

 

[Dan]

Oh I see what he was saying now. Yea I don’t see why that would be a problem. A brushing would reduce at the fitting but you just did it a couple inches out. Surely they’ll let that slide.

Look for a bushing they fit inside of the fitting and reduce there since you are cutting it out anyway.

i'll keep looking for the different options:

(1) 2" x 1.5" x 1.5" 'combo' tee
(2) 2" x 1.5" x 1.5" wye + 1.5" 45-degree elbow

will have to keep looking if i cannot go 2" tee --> 2" pvc --> 2" to 1.5" reducer --> 1.5" trap adapter. strange thing is i cannot find any product that fits this description

 

[Terry H]

https://www.plumbingsupplynow.com/2-x-1-1-2-x-1-1-2-pvc-dwv-combination-wye-1-8-bend-d502241

I’m not familiar with UPC but a 2” combination and a couple of bushings should satisfy it from what’s been said.

What you have done would pass here unless they didn’t like the 90s with the venting. You could always try it. The inspectors don’t know the book like you think they would.

 

[Jeff H Young]

I would have just used a 2 x2 x1 1/2 combi and ran with a 2 inch glue p trap. I dont like slip joints too much.

 

[Reach4]

thanks. UPC. so gotta cut that out tomorrow. all the references for the sanitary-tee laying on its 'back' was for water/solid draining rather than vent so I thought it was ok for a vent.

Could be worth asking your inspector. The regarding draining vs vent, the santee would be carrying drainage.

i'll keep looking for the different options:

(1) 2" x 1.5" x 1.5" 'combo' tee
(2) 2" x 1.5" x 1.5" wye + 1.5" 45-degree elbow

will have to keep looking if i cannot go 2" tee --> 2" pvc --> 2" to 1.5" reducer --> 1.5" trap adapter. strange thing is i cannot find any product that fits this description

What can't you find-- one of these?

https://www.supplyhouse.com/Spears-P502-251-2-2-1-1-2-PVC-DWV-Wye-and-45-Elbow-Combo
or

https://www.supplyhouse.com/Spears-P601-251-2-x-2-x-1-1-2-PVC-DWV-Wye

If you use the wye, you could pair that with a street 45.

 

[Gagecalman]

I'm not a plumber. Just trying to learn and understand.
If the metal drain on the left is 1-1/2" shouldn't everything be 1-1/2" not 2".
Doesn't using 2" reduce the size in the direction of flow which I thought was not allowed?

 

[wwhitney]

If the metal drain on the left is 1-1/2" shouldn't everything be 1-1/2" not 2".

That's correct. Someone (Terry?) labeled that photo after it was posted, my eye was not experienced enough to notice the size difference unlabeled. So based on the label, everything in the photo should be 1-1/2".

If the pipe on the left were 2", then the easiest thing to do is to transition from 1-1/2" to 2" at the banded coupling, so again all the plastic would be 1-1/2". If for some reason that was undesirable, then you could use a 2" x 1-1/2" x 1-1/2" combo for the vent take off, either as a single piece or as a 2" x 1-1/2" x 1-1/2" wye plus a 1-1/2" street 45. Both options are manufactured, it's just a question of what can be had.

Cheers, Wayne

 

[Dan]

That's correct. Someone (Terry?) labeled that photo after it was posted, my eye was not experienced enough to notice the size difference unlabeled. So according to the label, everything in the photo should be 1-1/2".

If the pipe on the left were 2", then the easiest thing to do is to transition from 1-1/2" to 2" at the banded coupling, so again all the plastic would be 1-1/2". If for some reason that was undesirable, then you could use a 2" x 1-1/2" x 1-1/2" combo for the vent take off, either as a single piece or as a 2" x 1-1/2" x 1-1/2" wye plus a 1-1/2" street 45. Both options are manufactured, it's just a question of what can be had.

Cheers, Wayne

thanks all for the feedback on my terribly researched work (but perhaps properly executed?). i thought the new pvc had to be 2" connecting into the galvanized steel. the two sections i'm replacing are:

(1) shower/tub vent (i'm using 1.5" pvc for the vent)
(2) bathtub drain

the shower/tub combo vent size is straight forward: 1.5" diameter minimum. i thought anything connecting to the 'drain' from the bathtub to be 2" pvc since all drains for bathtubs need to be 2".

just thinking about the bathtub drain meeting the galvanized section: is all that not needing to be 2" pvc? in other words is all that pvc connecting to the galvanized still considered a bathtub 'drain'? not sure what i'm missing: is it because its a shower+tub combo that i can do all 1.5"? thanks

 

[Dan]

Could be worth asking your inspector. The regarding draining vs vent, the santee would be carrying drainage.

What can't you find-- one of these?

https://www.supplyhouse.com/Spears-P502-251-2-2-1-1-2-PVC-DWV-Wye-and-45-Elbow-Combo
or

https://www.supplyhouse.com/Spears-P601-251-2-x-2-x-1-1-2-PVC-DWV-Wye

If you use the wye, you could pair that with a street 45.

seems i can't reduce down from 2" to 1.5" so i would need to get a combo that is 2" x 1.5" x 1.5" or a wye 2" x 1.5" x 1.5" with a street 45-degree as you mentioned.

or one option i'm still unclear on is a wye or combo that is 2"x 1.5" x 2" and use a trap adapter that fits direct into the wye/combo without the need for a 'reducer'?

 

[wwhitney]

Shower over a bathtub is considered a bathtub and can be a 1-1/2" trap and drain.

Is the galvanized pipe on the left 1-1/2"? If so, all the drains upstream of it have to be 1-1/2".

Cheers, Wayne

 

[Dan]

I'm not a plumber.

me neither, clearly. so the idea youre putting forth is that in the direction of flow the size of the pipe should never decrease? that makes sense, restricting volume means flow has to increase in speed or get backed up for the equivalent flow rate

 

[Dan]

Shower over a bathtub is considered a bathtub and can be a 1-1/2" trap and drain.

Is the galvanized pipe on the left 1-1/2"? If so, all the drains upstream of it have to be 1-1/2".

Cheers, Wayne

well this is the problem: i'm not sure what to call the size of the galvanized steel. it is ~1.25" inner diameter / ~1.75" outer diameter. but 1.5" solutions couplings fit it.

if everything in pvc needs to be 1.5, that makes my life a lot easier. i already have the coupling that fits the galvanized to 1.5" pvc (i used it for the shower vent in the attic). all i need to find is a 1.5" x 1.5" x 1.5" combo or wye + street elbow, correct? the schematic i will do below:

 

[Reach4]

me neither, clearly. so the idea youre putting forth is that in the direction of flow the size of the pipe should never decrease?

Almost never. One exception is the 4x3 closet elbow/bend.

I can think of another potential exception.

 

[Jeff H Young]

I may have misread pictures. The drain must never decrease in size as it travels downstream "choking it down" not allowed except for a closet bend may reduce