DWV Help

[RT520]

Hello, I’m hoping you guys can help an novice out with what I need for my DWV before I pour my shop floor. The plumber who I had originally lined up to do the work has basically told me he’s not going to get to it. I’m frantically trying to learn as much as possible to get this installed myself so I can move forward as this is supposed to be our home for the winter. There are no permits or inspections required in my area in Western Montana.


Behind my washer machine is where I would like to run my main vent up and have everything attach to there. So it’s not visible in my loft.

I’m not sure what’s best for venting my shower and toilet, I’ve seen where the vent is in between the two at an angle to the wall before going vertical.

Can both sinks on opposite walls share the same drain and vent?

my septic tank is approx 125’ away from the shop. I will need 2 45° to get out off the shops knock out as well as 2 45° to get to the inlet.

Yes, I know I should probably leave this to a professional but everyone else I’ve called is sold out till next year or won’t return my calls. My wife will not be happy with me if she has to live in a camper for the winter..

Thank you!

 

[Jeff H Young]

so how are you thinking of getting your vents to the main stack? its pretty basic , if you don't see a way an AAV might be an option. Yes sinks share the same vertical pipe.

 

[Sponsor]

 

[wwhitney]

Montana uses the UPC, so I don't think an AAV would be an option.

The UPC requires that the aggregate vent area through the roof be at least the area of the minimum size building drain, which is 3" for a residence with up to 3 WCs. So if you want a single roof penetration, it will have to be 3". Or you could use a 2", a 2" , and a 1-1/2", that has an aggregate area exceeding the area of a 3".

Below is an option for the below slab plumbing, red is 3" and blue is 2". Circles are risers out of the slab:

2" by the washer for the washer standpipe drain (with 2" vent above)
2" in the shower for the shower drain (I'm not experienced with underslab DWV, perhaps it makes more sense to box out a larger area and then for the rough just leave the horizontal trap arm stubbed out into the box, so you can fine tune the shower trap location later)
2" in the wall behind the shower (use an upright combo) for the 2" shower vent, which will wet vent the WC. The trap arm (pipe run from the shower trap to the vent takeoff) is limited to 60", so the vent takeoff may need to be closer to the shower than I drew.
3" for the WC drain, you'll need to locate your WC exactly for this.
2" for the two sinks (lavatory and kitchen?), which can share a vent above.

Then at an elevation of, say, 6' above the floor, the DWV will have just 3 vents in the 3 different walls: the washer standpipe (2"), the sinks (1-1/2" or 2"), and the shower/WC (2"). If you want just one 3" roof penetration located behind the washer/dryer, you can bring the other two vents up into the ceiling over the room shown, over to the washer vent, and combine all 3 vents into a 3" vent.

Cheers, Wayne

 

[wwhitney]

A few more comments:

Everything under the slab gets sloped at 1/4" per foot. So if the longest run from the septic is 28' (a guess), then the drain at that point will be at least 7" higher than the building drain's exit from the building.

The risers all turn up with LT90s (except for the shower vent, that's a combo). As drawn, the horizontal fittings are all wyes or 45.

The above doesn't address cleanout location(s), hopefully someone else can advise on that. That may mean changing some of the 2" line to 3" line to provide for a 3" cleanout above the slab. E.g. that would be easy to do with the shower vent, to put a cleanout there.

Cheers, Wayne

 

[RT520]

Thank you for the response. I figured it was a pretty basic system and made it more of a surprise when he said he wasn’t going to get to it.

Above the bathroom will be a loft so I can run my vents through the floor joist to the stack.

 

[Jeff H Young]

rt520 I would put a 3 inch clean out the good place would be a 3 inch cleanout in wall by shower . getting the vent over to near where wash mach. vent rises could be a challenge if useing solid wood joists, I beam joists are easy to drill and a 2 9/16th hole should be fine I. If hand digging your exact plan might vary a little with likely wanting not to dig as deep . less labor.
a few details that might help above , seems pretty doable to me

 

[RT520]

Is there a max distance I can run 3” pipe?

The main line will be 125’ long once I get out of the shop. I plan for a 1 clean out by the washer. 1 directly out side the shop and a 2 way clean out when I 45 to the tank.

 

[Jeff H Young]

we need max 100 ft between clean outs, putting a 2 way might help, I'd prefer regular c/o at mid way .

 

[RT520]

I talked with environmental health and I’m required to run 4” once I leave my shop. Should I run 3” inside and expand to 4” once I get outside or just run 4” from the start?

 

[RT520]

I talked with environmental health and I’m required to run 4” once I leave my shop. Should I run 3” inside and expand to 4” once I get outside or just run 4” from the start?

 

[RT520]

I talked with environmental health and I’m required to run 4” once I leave my shop. Should I run 3” inside and expand to 4” once I get outside or just run 4” from the start?

 

[Jeff H Young]

what happened to no permit or inspection? I'd run 3" inside 4 to tank

 

[Terry]

It's pretty normal to run up to three bathrooms with 3" and through the foundation, and then 4" to the main sewer or septic.
Venting is 3" through the roof, either one pipe, or sometimes several making up the total area of a 3" pipe.
Two 2"
One 1.5"
Equals the same area of a single 3" vent.

 

[RT520]

Well, my septic system needs inspected. Everything inside the dwelling doesn’t. I didn’t realize that they wanted to see from the house to the tank, I thought it was only from the tank to the leach field… I’m glad I called to double check.

 

[Jeff H Young]

rt520 the 3 inch inside and 4 to septic tank will be fine , gotta go with the flow (no pun intended) yea good you did call

 

[RT520]

Couple more questions for you guys.

Is there a max burial depth 4” pipe can be? There are some spots that I’m about 4’ down to run 1/4” to my tank.

How far below concrete should I have my interior pipe?