Vent/Waste Schematic Input

[stacking908]

Good morning All,

I am looking for some input on my vent and waste schematic. I am building my own house, I am not a plumber so would like you alls take on what I would like to do. I have attached a photo of what I have. Just trying to get an over all picture before I get into the details. I live in wild west of Arizona, the inspector is very relaxed, just about gets out of his truck with sandels on, were under 2018 International Plumbing Code.

Couple things I am stuck on:
1 - I am looking to have as few roof penetrations a possible small roof and putting solar panels up but I dont know if I can combine vents like this

2 - The kitchen sink is under a window on an exterior wall and the inspector said I could use an AAV instead of drilling through the king stud, wanted to see if this is the best solution

3 - Lastly on the upstairs wet vents my water closets are inbetween my shower and sink, before I have run the lav of the shower branch before it meets the w/c branch to wet vent; but with the tight space this isn't really possible, not sure I can run the lav with vent like I have it in the schematic.

Thanks for the input and if there is more I should change let me know. Ryan

 

[Reach4]

If you join the 2-inch lav drains to the shower trap arms before joining the toilet waste, that will make the wet venting right.

You can use an AAV for the kitchen, but the other way is to run the trap arm to the left or right to pick up a dry vent to the left or right of the window. How far is it to the left or right side of the window?

 

[Sponsor]

 

[wwhitney]

1) Combining vents is fine. If you have an attic space, you could combine the two 2" vents you show going through the roof into a single 3" roof penetration. If you get significant freezing weather where you are, it is normal to upsize each vent to 3" as it leaves the thermal envelope to reduce risk of frost closure.

2) If you want to avoid drilling the window king stud, then the two options are to go around it (route the trap arm in front of the king stud to a san-tee not under the window), which would take up more cabinet space, or use an AAV like you said. [There is also combination waste and vent, but that is more esoteric and acceptability varies by jurisdiction.]

3) No, the wet vents are not correct. For the drainage from the dry vented lav to act as a wet vent for other fixtures in that bathroom, you have to join it to the shower or WC first, and then the combined lav/shower (or lav/WC) joins the WC (or shower).

Also, the way you've drawn the shower make it look like the trap arm turns down before being wet vented. That is not allowed; the connection between the shower trap arm and the drain acting as a wet vent is the vent connection for the shower trap, and that vent connection must be within 2" vertically (maximum 2" of total fall) from the trap outlet.

Cheers, Wayne

 

[stacking908]

Thank you guys for the fast response. I will go with the AAV then if that is allowed. Good to hear combining the vents are fine, im good with two 2" vents out the roof, just didn't want four or more. So I have to fix the wet vents. Because of how my bathrooms are set up, picture attached. the Lav drain would have to cross over or really snake around the 3 inch w/c drain. I drew were the 3" drain comes up to the second story from first to see the bathroom layout.

Thanks again for your help

 

[Reach4]

Because of how my bathrooms are set up, picture attached. the Lav drain would have to cross over or really snake around the 3 inch w/c drain.

Lav drain pipe can cross behind the toilet tank in the wall, or or maybe behind the toilet drain under the floor. Neither seems like a lot of snaking.

I drew were the 3" drain comes up to the second story from first to see the bathroom layout.

I could not figure that out. Your isometric actually illustrates that? You know, you could have put an orange dot on the upst.jpg to illustrate that place.

It's just inconsequential semantics, but I would have written I drew where the 3" drain goes down from the second story to the first to see the bathroom layout. Your wording is not unique. I wonder if there is a common protocol for that. I guess if you are constructing, you work from downstream to upstream. In my head I think of a drain going from upstream to downstream.

 

[wwhitney]

If you are under the IPC, it permits horizontal wet venting for 2 bathroom groups at once. So you could install the DWV as below. Notes on the diagram:

1) This just shows the horizontal drains under the floor. The circles are vent takeoffs for the lavs; obviously each lav has a trap arm above the floor, which can go to a san-tee in the wall, with the vent going up and the drain dropping down to the horizontal segment drawn.

2) You don't show the direction of joists, so the layout is not optimized for actual installation. The point is to show the minimum pipe sizes and connectivity order for wet venting. (Well, the IPC allows 1-1/2" for showers, but 2" is more common).

3) Orange = 3", Blue = 2", Green = 1-1/2".

4) Everything except the right hand lav is wet vented by the left hand lav and its dry vent. The connectivity restriction is that other fixture's fixture drain join that that wet venting lav drain one at a time, individually.

5) I show the right hand lav going directly to the stack, e.g. a separate san-tee or wye above or below the one for the branch drain. You could of course bring the lav drain to the left into the room, then turn towards the bottom of the page and wye into the 3" branch drain, if you don't want two separate stack connections. That would just involve more horizontal bends.

Cheers, Wayne

 

[stacking908]

Wayne, Amazing thank you so much! Joist running left to right so this will be good. The washing machine drain there, should I tie that into the Orange 3" branch and can I connnect its vent to the wet vent in the attic? Or should I runn the washer drain to the stack?

 

[Reach4]

I connnect its vent to the wet vent in the attic?

There is no wet vent in the attic. A wet vent only exists below where the drainage is added. So yes, you can join the vents in the attic.

The washing machine drain there, should I tie that into the Orange 3" branch

WM standpipe drain could joint the 3 inch downstream of the toilet.

 

[stacking908]

Ok yes sorry about that. Last question, the vent pipes should be 1-1/2" up the stud cavity and then 2" when combined or should I run 2" vent pipe from the start? Thank you guys so much for the help. Really appreciate it very much!

 

[wwhitney]

Joist running left to right so this will be good.

OK, that will minimize drilling of joists for a 3" pipe, but you will still need to drill some because the two WCs are offset up-down the page. You will likely want the 3" drains to cross perpendicular to the joists at those points, so not what I drew. If your joists are 2x12 or I-joists, you can likely drill a 3.75" hole without repairing the joist, but if they are 2x10s or smaller, you would need to use a joist reinforcement for a 3.75" hole. And of course a 3.75 hole doesn't give you must wiggle room, so you'll have to align your holes closet to perfectly to get the necessary slope (IPC allows only 1/8" per foot on 3", but 1/4" per foot is better if you have room).

The washing machine drain there, should I tie that into the Orange 3" branch

As Reach4 stated, that connection would be OK downstream of 2nd WC. That 2nd WC connection is where the hoirzontal wet vent ends, and any drain carrying laundry standpipe drainage may not be part of a horizontal wet vent. The washer standpipe drain will need its own dry vent takeoff, just like all the other traps above the floor (the lavs).

Ok yes sorry about that. Last question, the vent pipes should be 1-1/2" up the stud cavity and then 2" when combined or should I run 2" vent pipe from the start? Thank you guys so much for the help. Really appreciate it very much!

1-1/2" is all the IPC requires for each of the 3 dry vent takeoffs. There's something to be said for upsizing the left hand lav vent and drain (starting at the vent takeoff, i.e. the san-tee outlet) to 2", but it is not required by the IPC. If/when you combine two of the vents, going to 2" minimum would similarly be a good idea, although I believe also not required (would have to double check). And as stated earlier, if you're in a cold climate, upsizing any vent to 3" just before it leaves the thermal envelope is a good idea and possibly required.

Cheers, Wayne

 

[Reach4]

Ok yes sorry about that. Last question, the vent pipes should be 1-1/2" up the stud cavity and then 2" when combined or should I run 2" vent pipe from the start?

See table on page 4 of https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf
The number of DFU (drainage fixture units) identify how far 1.5 inch vent pipe can run. I have to think 1.5 is going to turn out to be good.

 

[stacking908]

Wayne I have enginnered 12" I-joists and I looked up holes and that should be an issue with the size hole. I will run a 2" vent for that left hand Lav, per the table I can run 1-1/2" but will run 2", that wall only i made 2x6. Also not in a cold climate, live in the desert. Thanks so much for your help guys

 

[wwhitney]

Wayne I have enginnered 12" I-joists and I looked up holes

Ah, then you likely have the luxury of making 4" - 4.5" holes.

[In solid sawn joists, the prescriptive hole size limit is 1/3 of the joist depth; for a 2x12 that is 11.25" actual depth, that comes out to 3.75", hence the need to fit a 3.5" OD pipe (3" nominal DWV) in a 3.75" hole when working with solid sawn 2x12s.]

Cheers, Wayne