Help with under slab plumbing for new house

[jeffesonm]

I'm building a house (my first!) and will be doing the plumbing (among other trades). You all were so helpful making my first plumbing project a success so thought I'd try my luck a second time.

It's a relatively simple ~1152 sq ft, one story, 2 bed 2 bath in Austin Texas. Slab foundation into which I soon need to place the plumbing. All will be inspected and we're on 2015 UPC.

See proposed layout below. 4" line coming in from outside, will be sleeve going through foundation grade beam sleeved in a section of 6" pvc.

Bath 1: 4" off the main line going to wc, flange set 12-13" off 2x6 wall. 2" line coming off to shower drain, serving to wet vent wc. 2" p trap for shower drain set in ~12x12x12 box filled with sand during slab pour. 2" line coming off to lav drain, serving to went vent shower. Vent continues up and out roof, or maybe out sidewall (and then up to roof, outside building.). Upturned wyes for all these wet vent connections.

Washer: 2" off main line, 2" running up to AAV, 2" trap, 2" standpipe up into one of those wall box thingies.

Bath 2: 4" off main line. Sanitee connecting to lav, then up to vent for lav. 4" line continues to wc, flange as described above. 4" line continues past, with 2" coming off to serve tub. Again p-trap in 12x12x12 box so I can wiggle that around. 2" vent up, connects up with lav vent, heads out the roof.

Kitchen: as drawn, 2" sink drain runs ~4' and drains into 2" shower vent, but I'm feeling like maybe that's not allowed?

Any comments? Apart from measure and remeasure 10x, any other slab specific stuff? So far I've got sleeve through foundation wall and a few wraps of sill plate foam where pipe comes through slab.

Will have some pex/water line questions eventually but would love to get the dwv side sorted out first. Thanks in advance!

Jeff

 

[Reach4]

Feed the kitchen sink into the stream after the bathroom stuff.

You should mark the kitchen sink and other stuff on your pipe drawing.

All horizontal 3-port fittings are wyes or combos.

 

[Sponsor]

 

[jeffesonm]

Thanks... added some more labels to diagram.

For kitchen sink, do you mean after like the blue dashed line? Was hoping to not have a separate vent for kitchen sink. I had hoped to use the bath 2 group vent to drain/vent kitchen sink but that seems dubious. I suppose I could do AAV for kitchen sink too.

 

[Reach4]

For kitchen sink, do you mean after like the blue dashed line?

Yes.
No way around a vent for a kitchen sink, but that vent could be an AAV. Further, you probably have to put the lavatory upstream of the shower. Not sure if the toilet has to be after the shower. In UPC it does, and IPC it doesn't. You use NSPC. http://epubs.iapmo.org/NSPC/NJ2018/mobile/index.html

 

[wwhitney]

No AAVs under the 2015 UPC, unless Austin, TX has amended it.

Also, the UPC requires the aggregate area of vents through the roof to be not less than the minimum size building drain for the fixtures present. That would be 3", so you'd need one 3" vent, or a combination such as (2) 2" vents and a 1-1/2" vent.

Cheers, Wayne

 

[Jeff H Young]

Why an aav on washer machine? new house is there a beam or something? Cleanouts needed. the bathroom by the kitchen I would continue the drain out side for c/o who wants to bring a snake thru house.
Also not enough venting for a 4 inch sewer . lastly as a general workmanship My opinion is avoid aav's unless there is a reason not to vent out properly, not that big of a deal but why use one any where in this house?

 

[wwhitney]

Suggestion on Kitchen/Bath 2: the kitchen sink will need it's own vent, but you can wet vent the tub and toilet. Possible layout (arbitrarily calling North the top of page):

Vanity 2" drain hit slab and goes NE to hit a wye that is just N of toilet flange. Coming into W inlet of wye is tub drain. 2" drain proceeds E from the wye.

WC drain goes SE from flange to get S of vanity, then 45s E, then 45s NE and hits wye in lavatory drain just past tub/lavatory wye.

Kitchen sink drain goes E and turn NE to join bath 2 drain after WC.

Cheers, Wayne

 

[Jeff H Young]

I dont think the kitchen would be allowed upsteam of the went vented system

 

[Tuttles Revenge]

This is how I would design the plumbing for that house.

 

[jeffesonm]

Here is a kinda poor rendering of the interior of the house, taken from the S end in between the living and dining areas and looking back towards the N. Imagine a regular house, but you raised the roof up 2.5' and put a row of 2.5' tall windows all the way around in the space created. Exposed roof trusses and roof deck. There will be ceilings over top of the bathrooms and bedrooms, but then there's clear space above those ceilings and below the roof assembly.

All that is to say I really want to minimize any obstructions, pipes, etc in that 2.5' space. In addition I cannot really route much through the walls to the roof because in between the windows are structural columns made of up (3) 2x6 on the flat, packed out to 5.5". So that's why trying to minimize the vents via AAVs which as per above are not allowed in 2015 UPC (Austin has some local amendments but I saw no mention of AAV)

Ideally I can manage just two plumbing vents in total (sounds like 2x2" would cover my 4" sewer) one each on the E and W walls. I'd route them tight against the wall in the space between the windows.

 

[wwhitney]

All that is to say I really want to minimize any obstructions, pipes, etc in that 2.5' space.

So aesthetically you'd like it completely empty? It's not just enough to dress up the pipe with a pretty surround?

That will be hard to do. At the fixture level, you need at least 4 vents: one for each bathroom group, one for the laundry, and one for the kitchen. Now, once you get above the flood rim of the fixtures involved, you could combine the vents within the partition walls before hitting the 2.5' open space. So you may be able to combine the kitchen with bath 2 and laundry with bath 1, if you want to run alot of 1.5" vent pipes around the partition walls through all the studs. [The bathroom groups need 2" vents due to the toilet and wet venting, but I think both the kitchen sink and the laundry can be 1.5" (worth double checking), so it would be easier to bring the 1.5" vent to the 2" vent, rather than vice versa.]

In addition I cannot really route much through the walls to the roof because in between the windows are structural columns made of up (3) 2x6 on the flat, packed out to 5.5".

Perhaps too late now, but at the design stage it would have been worth adding a 5" empty stud bay in two locations to accommodate the vents.

Ideally I can manage just two plumbing vents in total (sounds like 2x2" would cover my 4" sewer)

Even though you have a 4" building drain, you could plumb the whole house with a 3" building drain, so 3" aggregate vent area is all you need. However, it's area, not diameter. So (2) 2" vents is not enough, area is proportional to the square of diameter, and 2*2 + 2*2 < 3*3. Perhaps when you combine a 1.5" vent with a 2" vent you can make the combined 3" vent and that would count.

Cheers, Wayne

 

[Tuttles Revenge]

You can do all that if you get your designer to communicate with your engineer and they chat with the plumber about how to get a 3" or equivelent vent through the roof. Aesthetics are not really a high priority in the UPC.

Call your inspector to see what they expect and what you want to do. Sometimes you can figure something out. Maybe move the washer dryer to an exterior wall where the vent can travel to. Sometimes a thickened wall in one room can hide or help route a pipe.

 

[jeffesonm]

First, thanks all, I really do appreciate the timely and thoughtful feedback.

Fortunately (or unfortunately) I am both the designer and the plumber on this project. I do have a legit engineer who specified the 2x6 stud packs to transfer shear from the area above the windows to the area below, since for most of the building that's the only bit that connects the two.

I'll talk to him and see if one of those can be (2) 2x6 with a 2x3 spacer, which would accommodate a 2" vent in the middle. If I can tie together Bath 2 vents and kitchen vent in the wall and run one 2" up this cavity, that'd do the trick. It's just under 4' from kitchen sink to adjacent partition wall, so I was figuring I could run the 2" trap arm through the corner cabinet to catch the drain/vent there.

That leaves Bath 1 / washer. If I could get them all tied together and run one one 3" up the side of the wall hugging a column between windows, I'd be happy with that. Also this East side of the house/lot is completely out of the way/not visible, so running out through the sidewall and then up to the roof is another option.

 

[Jeff H Young]

now i see why you wanted aav, consult with inspector might allow some compromise

 

[jeffesonm]

 

[jeffesonm]

I decided 3” seemed fine for a 1150 sq ft 2/2. Hopefully that is okay.

Any glaring errors before I put this all together for real?

 

[Reach4]

Bath 1: UPC-- Must vent shower before toilet. Then no additional vent needed for the toilet.

Kitchen waste already vented I presume.

 

[wwhitney]

Your connectivity and fittings selection looks good to me. A few comments:

- On the tub/shower in the first picture, you could turn the bath trap 45 degrees and use a 45 instead of a 90. A very minor improvement.

- Where's the vent takeoff between the tub/shower and the WC in the first picture?

- I can't always tell the difference in a picture between medium turn 90s and long turn 90. So just remember you can only use a medium turn 90 as a drain when the drain turns from horizontal to downward (vertical).

Cheers, Wayne

 

[Jeff H Young]

Im seeing problem on bath 2 tub improperly vented Im calling it bath 2 because thats what the floorplan calls it (by the kitchen) . All of my experiance has been upc and here our inspectors usualy cut no slack on clean outs required, so be aware that both bathrooms require end of line clean outs minimum one pipesize smaller so for 3 inch that would be 2 1/2" minimum Ive never gotten away with 2 " So I see that as a major issue. On bath 1 I would run 3 inch all the way out the side of footing and put a c/o out side in ground ( as I hate inside cleanouts for mains). obviously bath 2 needs adressing the c/o as well in my opinion. I know many places seem to think pulling a toilet is a good way , to way Ive been made to plumb its not an option. Looks good I think these changes really need looking at though

 

[jeffesonm]

Thanks for the feedback, I did in fact forget the vent take off between shower and wc on bath 2 (first photo.). Got that in there now.

That 2" long sweep 90 at the bottom of photo 1 is the kitchen drain... it will continue vertically where trap arm will connect and then vent will continue up.

Re: cleanouts... I suppose I could continue both 3" pipes out either wall although that would be kind of ugly on the W side, and near what will be the "front" door. Alternatively I read 707.4 exception (4) to suggest that a two way cleanout outside the building at sewer exit would also suffice (although presumably much less effective)