First time drain/vent rough-in "pre-inspection"?

[Kurt Granroth]

I'm about to install all of the rough-in plumbing for the above-slab drain and vent system for the first time and would like a "pre-inspection" by knowledgable pros. Don't assume I know something that's not shown or said, since I'm strictly DIY. Absolutely tell me about any code violations... but in addition, also tell me about any better ways to do things, if they matter.

This is a small one bedroom and one bath home. The bathroom has a washing machine hookup, a toilet, a lav, and a shower. The kitchen has a sink. It also has an island with a stub for a drain, but that'll be capped off since that's just there for future-proofing.

All of the pipes are 2" ABS unless otherwise specified. All vents combine to one stack vent that exits the roof. All horizontal pipes will be sloped 1/4" per foot (not shown in the model since hard to do in SketchUp).

First up is the bath. Each drain has a clean-out -- shown as a sani-tee here only because I can't find a SketchUp component of a "test tee".

The washer clean-out is at 14" above the floor. The horizontal part of the p-trap is 17" above. The vertical drain above the p-trap is 24", leaving the washer outlet box 42" above the floor. The washer vent uses a 90 degree vent-tee and an upside-down sani-tee to connect to the main vent.

The main vent has 3" clean-out facing in the laundry closet, also 14" above the floor (to be consistent with the washer clean-out). It reduces to 2" after that and everything else is 2" that follows.

The lav drain is 22" above the floor, to hit ADA recommendations (this house shall be ADA-compliant). The clean-out is just below at 17". It connects to the main vent using a series of 45 degree angles (to get around a window), a 90 degree vent-tee and an upside-down sani-tee.

The shower vent has a clean-out 18" above the floor in the utility room behind it. It connects to the main vent in the attic via a 90 degree vent-tee and a wye on its side.

The main vent continues on with a couple 90 degree vent-tees and exits the roof with 12" showing above deck.

The kitchen sink drain is 14" above floor with a clean-out just below. It uses a bunch of 45 degree angles to work around quite a few obstacles.

NOTE: I'm seriously considering ditching all of this in favor of an air-admittance valve (AAV) like a Studor Mini-Vent. That would be tee'd on the sink drain stub-out and then literally none of the vent would exist. Opinions?

 

[wwhitney]

A few comments by a full time DIY, nothing major:

It's important to know which plumbing code you are under, there are two main ones (IPC and UPC) and at least one more (NSPC). It appears Arizona is under the IPC, so my comments are based on that. Please confirm.

You could eliminate the toilet vent and perhaps the shower vent by wet venting the bathroom group. That depends on how you run the drains under the slab which aren't shown. If you post a Sketchup of the drains, then we could comment on those, as well.

What you are calling a "90 degree vent-tee" is just a "vent 90", it's not a tee. You aren't required to use vent 90s on the vent, you just have the option. You can use medium turn 90s, and last time I did this, they were cheaper. So I only use a vent 90 when I really need the reduced radius.

You definitely have more cleanouts than are required, but they don't do any harm. The ones under the sink are particularly redundant, since if you have a slip joint trap with a trap adapter on the trap arm, you can easily remove the trap for rodding the drain.

Cheers, Wayne

 

[Sponsor]

 

[Kurt Granroth]

A few comments by a full time DIY, nothing major:

It's important to know which plumbing code you are under, there are two main ones (IPC and UPC) and at least one more (NSPC). It appears Arizona is under the IPC, so my comments are based on that. Please confirm.

You could eliminate the toilet vent and perhaps the shower vent by wet venting the bathroom group. That depends on how you run the drains under the slab which aren't shown. If you post a Sketchup of the drains, then we could comment on those, as well.

What you are calling a "90 degree vent-tee" is just a "vent 90", it's not a tee. You aren't required to use vent 90s on the vent, you just have the option. You can use medium turn 90s, and last time I did this, they were cheaper. So I only use a vent 90 when I really need the reduced radius.

You definitely have more cleanouts than are required, but they don't do any harm. The ones under the sink are particularly redundant, since if you have a slip joint trap with a trap adapter on the trap arm, you can easily remove the trap for rodding the drain.

Cheers, Wayne

Thanks for the comments, Wayne!

I'm actually not sure which plumbing code is active in my city. I tried to track down all of the differences that appear to matter between IPC and UPC and implement whichever was more restrictive. My understanding is that IPC requires a "main vent" that travels from the sewer to the exterior while UPC does not -- so I created a main vent.

I didn't show the under-slab drains because those already exist; were installed by pros; and were already inspected and passed. If showing them will allow for even better advice for the above-slab bits, then please let me know and I'll post screenshots of the model for that part, too.

The excessive cleanouts was on the advice of a plumber who I consulted for tips prior to doing anything. He said that excluding them will absolutely fail an inspection but that they are nearly always drywalled over around here and the plumbers just remove the trap and go through the drain.

Thanks for the correction on "90 degree vent-tee" -- it's definitely not a "tee" so not sure why I was thinking that. Good to know that they are more expensive! I may go with medium 90s after all, in that case.

 

[Kurt Granroth]

Here is what the kitchen sync AAV layout would look like if I went that route. I'm concerned that the kitchen sync vent simply goes too far and around too many obstacles, unnecessarily.

2" ABS drain through floor connects to "test tee" for clean-out, then medium 90 connecting to sani-tee pointing upwards (flow going back towards drain). 6" minimum pipe up from sani-tee to Studor or Oaty AAV.

Thoughts?

 

[wwhitney]

I'm actually not sure which plumbing code is active in my city.

https://www.gilbertaz.gov/departments/development-services/plan-review-inspection

I tried to track down all of the differences that appear to matter between IPC and UPC and implement whichever was more restrictive. My understanding is that IPC requires a "main vent" that travels from the sewer to the exterior while UPC does not -- so I created a main vent.

No, that's not required for a house. The IPC just requires that at least one vent exit the roof, and the size has to be at least half the minimum size building drain for the house.

I didn't show the under-slab drains because those already exist; were installed by pros; and were already inspected and passed. If showing them will allow for even better advice for the above-slab bits, then please let me know and I'll post screenshots of the model for that part, too.

They certainly would be required if you have any interest in wet venting the bathroom. And you should probably post them regardless.

2" ABS drain through floor connects to "test tee" for clean-out, then medium 90 connecting to sani-tee pointing upwards (flow going back towards drain). 6" minimum pipe up from sani-tee to Studor or Oaty AAV.

Sanitary tees can not be used in drainage or for vent take offs "on their back," you'd use a combo for that. Or you could (a) jog out of the wall with two 45s, then an upright sanitary tee as normal or (b) put in a wall box for the AAV, so you could just have the sanitary tee in the wall. Not sure how (b) would work out with the heights and the kitchen sink blocking access.

Cheers, Wayne

 

[Kurt Granroth]

Here's the existing (installed by plumbers and already passed inspection) under-slab drain system:

It comes it from the sewer as 3" ABS and stays that way only as far as the toilet (and stub of main vent). Everything else is 2" ABS.

The bath wall has the washing machine drain, toilet drain and main vent, and lav drain.

The shower drain and vent are to the right of the main drain.

There is a stub out for a kitchen island drain, but it is capped.

The kitchen sink is a simple 2" ABS stub-up.

 

[Kurt Granroth]

Sanitary tees can not be used in drainage or for vent take offs "on their back," you'd use a combo for that. Or you could (a) jog out of the wall with two 45s, then an upright sanitary tee as normal or (b) put in a wall box for the AAV, so you could just have the sanitary tee in the wall. Not sure how (b) would work out with the heights and the kitchen sink blocking access.

Are you sure? I know that it's forbidden to use sanitary tees on their back for drains and wet vents, but I've seen many references to using them on their back for dry vents -- like would be the case for the AAV. These references (and pictures) can be found on sites like Fine Homebuilding and even these forums...

 

[wwhitney]

Are you sure?

Hmm, now that I double check, I'm not sure. It is definitely prohibited under the UPC, which says in 905.3 "Vents less than 6 inches (152 mm) above the flood-level rim of the fixture shall be installed with approved drainage fittings, material, and grade to the drain." That would apply to the takeoff, so it would have to be a combo.

But I checked the IPC, and its version of that section (905.4) doesn't have that language. So maybe it is allowed under the IPC. Yet I had gotten the impression here that it wasn't. I would say a combo would be a better practice, although for an AAV, it hardly matters.

Cheers, Wayne

 

[Reach4]

Thoughts?

Logically IMO, the santee on its back should be allowed for the AAV.

Consider Rectorseal Magic Trap. Even UPC approved, much to the horror of some (parenthetically).
https://rectorseal.com/product/magic-trap/ That would be allowed. If that is allowed, so should what you propose. But if it is not acceptable to use the santee on its back, consider using the Magic Trap.

https://www.supplyhouse.com/Rectorseal-97402-Magic-Trap-Tubular-Fitting-w-Tee