DWV Rough In Plumbing Help

[wxtrender]

Please look at my drawing and comment if I am doing this correctly. I am in Pennsylvania and our building codes are the Uniform Construction Codes which basically refer us to the 2009 International Codes issued by ICC. So I have read over the international plumbing code and in particular Chapter 3 & 7 which deals with most of what I am looking at here.

I want to add a bathroom (WC & Lav + 1 additional remote sink) in a heated pole barn which will have a 6" slab on grade floor.

The picture is a top view only.

At the bottom of each stack and the WC I was going to use 90 deg drain elbows to go from vertical to the horizontal lines in the pictures. I was planning to wet vent the WC using the drain/vent stack that the bathroom sink will connect to and then proceed out the roof. The remote sink in the middle of the barn was going to connect to its own drain vent stack and continue out the roof.
All drain lines will slope at 1/4" per foot toward the septic.

Does anyone see anything wrong at this point?

Couple of additional questions...
1. Since the floor has not been poured yet I have about 10-12" from the top of the concrete to the undisturbed earth. Do I need to set these pipes in a trench filled with sand? Or just pile up sand on grade for the slope? Total horizontal distance is about 30 ft to side wall so I need a drop of 7.5". Or can I use the gravel we are putting down under the concrete to support the piping and maintain the slope? Does the whole pipe need to be covered in sand as well? If I do need sand underneath...how much is enough? The soil has lots of broken bits of shale 1-3" in size.

2. The code mentions freezing but section 305.6.1 Sewer depth does not give any measurements...is that because there aren't any?

Thanks

 

[hj]

re,; 1,4, & 5, there are three different "drain elbows" and for your purposes those three have to be "long radius" quarter bends. Since your floor is almost a foot above the undisturbed dirt that means it must be that far above the outside grade also. If so, then I would NOT do it the way you show, and WOULD excavate a trench about 10" below grade. Then connect the toilet into the 3" riser at the lavatory.

 

[Sponsor]

 

[wxtrender]

re,; 1,4, & 5, there are three different "drain elbows" and for your purposes those three have to be "long radius" quarter bends. Since your floor is almost a foot above the undisturbed dirt that means it must be that far above the outside grade also. If so, then I would NOT do it the way you show, and WOULD excavate a trench about 10" below grade. Then connect the toilet into the 3" riser at the lavatory.

Actually the grade outside the building will be backfilled just a bit below the top level of the inside concrete floor.
As far as connecting to the Lav riser, would I connect from the horizontal run from the toilet into the 3" Lav stack, using a sanitary tee? The sink would then connect into the same stack a few feet higher also using a sanitary tee?

If I left the design as originally sketched above does it still meet code?

 

[hj]

yes, and yes, but I prefer my way and use it whenever there is adequate depth for the main line. It eliminates that "long" 3" horizontal run from the sink which will NEVER have enough flow to be "self cleaning". And you eliminate that "corner" at #1 by installing a 45 at #2.