Utility/Master drain and vent design

[Grizzle]

Gonna redo the franken-piping in my addition.

It has a utility/half-bath, and master w/double vanity, over a crawlspace.

The 3" main vent and 2" vented sink drain are in the 2x6 wall separating the two rooms.

I'd be grateful for any advice you guys can give on my design. My local code is UPC:

 

[wwhitney]

Comments:

- I'm going to assume that all your sinks are lavatories, as you are using them for wet venting. If one of them is not, that's a problem. So for the 2x2x2 san-tee in the lower right, you really want a 2x2x1-1/2 san-tee, but you can just put a 2x1-1/2 bushing into a 2" san-tee.

- For the 2" double lav drain to wet vent the shower, the shower trap arm is limited to 2" of fall (and 60" of length), and the trap arm extends from the trap outlet to 2" combo where the 2" double lav drain joins the horizontal branch. So you can't use a 45 on the branch inlet of your 2" combo cleanout fitting, you need to lower the shower trap (or raise the 2" horizontal branch) and roll the 2" combo cleanout fitting to be horizontal.

- I guess the dry vent configuration for the upper (on the page) WC is OK, but it's a bit weird. Seems like it would be more straightforward to take the 3" dry vent off the WC drain. I.e. have the WC drain hit a san-tee, and then either a 45 or a LT90 on the san-tee outlet to hit a vertical or horizontal 3" wye.

Otherwise looks good to me.

Cheers, Wayne

 

[Sponsor]

 

[Lukewalker64]

View attachment 96373

This is a cool drawing. What software did you use?

 

[Grizzle]

Comments:

- I'm going to assume that all your sinks are lavatories, as you are using them for wet venting. If one of them is not, that's a problem. So for the 2x2x2 san-tee in the lower right, you really want a 2x2x1-1/2 san-tee, but you can just put a 2x1-1/2 bushing into a 2" san-tee.

- For the 2" double lav drain to wet vent the shower, the shower trap arm is limited to 2" of fall (and 60" of length), and the trap arm extends from the trap outlet to 2" combo where the 2" double lav drain joins the horizontal branch. So you can't use a 45 on the branch inlet of your 2" combo cleanout fitting, you need to lower the shower trap (or raise the 2" horizontal branch) and roll the 2" combo cleanout fitting to be horizontal.

- I guess the dry vent configuration for the upper (on the page) WC is OK, but it's a bit weird. Seems like it would be more straightforward to take the 3" dry vent off the WC drain. I.e. have the WC drain hit a san-tee, and then either a 45 or a LT90 on the san-tee outlet to hit a vertical or horizontal 3" wye.

Otherwise looks good to me.

Cheers, Wayne

@wwhitney

Wayne, thanks for the feedback. Very much appreciated.

I've attached an updated drawing that includes some existing structures for spatial context, plus a rough floorplan.

Per your advice:

- Item 1: I made the half-bath san-tee 2x2x1.5. Is that ok for a large, single-basin type sink (ie: farmhouse)?

- Item 2: I lowered the shower trap so the arm enters the combo horizontally. Distance from the trap to the double lav combo is roughly 40". Does that work?

- Item 3: ...if I understand, you'd basically move the 3" dry vent over to the blue tee I added on the toilet (WC) drain, and get rid of the 3" combo?

Other questions/comments:

> Do I actually need the lav vent that's highlighted in red?

> A san-tee on it's back is OK for dry venting?

 

[wwhitney]

- Item 1: I made the half-bath san-tee 2x2x1.5. Is that ok for a large, single-basin type sink (ie: farmhouse)?

All the sinks I've seen take 1.5" traps, so that's certainly fine. The question is whether you can reasonably call it a lavatory, so that you can use it to wet vent the WC, as you are doing. I figure if it's in a half bath and isn't just a bare bones laundry/utility sink style, you can call it a lavatory. But that's definitely a judgement call that your AHJ might feel differently about.

- Item 2: I lowered the shower trap so the arm enters the combo horizontally. Distance from the trap to the double lav combo is roughly 40". Does that work?

Yes. That distance is measured along the run of the pipe. The fall is also limited to 2".

Item 3: ...if I understand, you'd basically move the 3" dry vent over to the blue tee I added on the toilet (WC) drain, and get rid of the 3" combo?

Yes, that's the connectivity pattern I'm suggesting, although if you didn't want to move the 3" stack in plan, there are piping/fitting options that would work with the stack in its current location.

> Do I actually need the lav vent that's highlighted in red?

100% yes as shown. There are options for using a single dry vent takeoff to vent both vanities (it would dry vent the upstream one, and wet vent the downstream one), but they are more complicated and the separate dry vent takeoffs is probably simpler. The two dry vent takeoffs from the two vanities may join or go horizontal at any elevation at least 6" above the respective flood rim levels.

> A san-tee on it's back is OK for dry venting?

Not under the UPC, you need to use a wye or combo.

Cheers, Wayne

 

[Grizzle]

This is a cool drawing. What software did you use?

@Lukewalker64 - Thanks. I used Sketchup.

I Started with the free version to create a scale model of the building structure (thanks, pandemic). But I recently gave in and upgraded to Sketchup "Pro" (aka: paid) so I could gain access to their "3D Warehouse", which includes the PVC pipes and fittings i used in the design.

 

[RJick]

I just signed up to sketchup and went to the 3d warehouse but am having trouble finding
the fittings you used. Where are the pipe fittings and what should I search for.
Thanks
Rick

 

[Grizzle]

I just signed up to sketchup and went to the 3d warehouse but am having trouble finding
the fittings you used. Where are the pipe fittings and what should I search for.
Thanks
Rick

Sorry for the delayed reply...

I searched for "PVC fittings". Be sure to switch to the "Models" section. You should see quite a few collections there.

I pulled parts from a couple of collections, one called "PVC Pipe fittings":

...and another called "ABS DWV or PVC Fittings":