Waste line and venting advice for a slab on grade home

[dylannic]

Hi, hoping to get some advice in regards to this small slab on grade home, just wondering what my best options to minimize the footprint of waste lines under slab as well as venting overhead as it will be within a cathedral ceiling exiting a shed style roof (Atlantic Canada). My limited thought process of this was to have 2" ABS from the washing machine to a sanitary tee (venting vertically in the wall) with another sanitary tee above the previous where the sink will drain into. This will drop down to a 3" pipe, under slab, picking up the tub further down ( which will utilize the first vent). The toilet will branch into this 3" line but will have a vent through the slab just past the bend of the toilet, travelling up the interior wall and connecting to the previous vent in the ceiling and out the roof through a 2" pipe. Finally this will continue to the kitchen sink and will be vented separately with 2" pipe through the roof, furthermore the drain will continue into a 4" pipe and will exit beneath the slab to the septic tank. Hope that made some sense and I would appreciate any comments. Thanks. Also these will be buried at 3"+ below the bottom of the slab along with sleeved pex water lines.

 

[Reach4]

I think what you show would fly with US codes, if your drain pipes after the lavatory sanitary tee are 2 inch before the toilet, and 3 inches after. If you removed the separate toilet vent, it still works. So I suspect it is allowed in Canada also.

 

[Sponsor]

 

[dylannic]

Thanks, that's good to hear. Is it ok to use 3" pipe from the Sani tee of the lav to the toilet under the lab instead of the 2", I was just a bit nervous putting anything but 3" other than 2" from the tub to main line, I think that run is about 10' to the toilet back to the lav.

 

[Reach4]

Bigger is OK.

 

[dylannic]

Ok, thanks. One last question should I be going with 4" under the slab or is 3" fine up until it exits the building at 4" to septic?

 

[Reach4]

Four inches under the ground sounds shallow to me. I picture Nova Scotia as cold in winter.

 

[dylannic]

It is very cold in the winter, I'll stick with 3" then. Where it leaves the house I'm guessing as that has to meet the septic tank the pipe will not be bellow the frost line.

 

[Reach4]

Are you maybe thinking feet rather than inches? I don't know much about how deep it needs to be, but before you go with 4 inches, get more information.

 

[GReynolds929]

I think he's asking about pipe size not pipe depth.

 

[Reach4]

I think he's asking about pipe size not pipe depth.

Oops.

https://novascotia.ca/nse/water/docs/OSTG_03-Section03-TechGuide.pdf

June 2013 42
3.2 BUILDING SEWERS AND EFFLUENT LINES
A building sewer for a single unit dwelling, which is defined as the part of the building
drainage system carrying sewage that extends from the septic tank or public sewer to a point
one metre out from the foundation wall, shall be a 100 mm diameter pipe, c

So that means 4 inch to the septic tank I think. You may be able to use 3 inch under the floor.... don't know.

https://novascotia.ca/nse/wastewater/regulations.tech.guidelines.asp links to https://novascotia.ca/nse/wastewater/sewagedisposalguide.asp

 

[dylannic]

Thanks very much for finding those links.. Just had a read and it looks like the min depth of the tank can be at 6" plus probably another 12" for the depth of the inlet with rigid foam on top of the exterior abs. So all in all 24" pipe depth at the tank, if tank is buried deeper and the grade is a bit higher up near the house, I'll probably go with placing the 4" pipe 6" below the thickened edge (23" bellow finished grade) of the slab exiting the building and follow the grade down. I would also like to sleeve the pex water lines beneath the slab at the same depth as the waste lines, is abs a suitable sleeve for pex to? Hydronic pex pipes will be at the bottom of the 4" slab, these will all run under a load point across the interior of the slab so it will go from 4" slab to 18" deep by 2' wide trench carrying a 10' ICF wall, the water lines to the fixtures can go beneath this but the hydronic has to be on top, is it ok to run each line 4" below the icf wall if sleeved, or is down and up better.