New Build in USVI

[DFisher15]

Hi Everyone,
I have been a long time lurker as I have done several remodels and flips over the years but I'm starting a new build in St. John USVI and wanted to get everyone's feedback as I want to start ordering materials while I wait for my permits. USVI follows all stateside codes so there is nothing special about it. I will be doing the work myself as a home owner and this is my first time doing stab on grade plumbing so I want to get it right. This is a simple single story home with one bathroom, a washer and dryer, and kitchen sink w/ dishwasher. I have attached the pertinent section of my plan as well as my crude top and side profiles. It would be great to get any advice you may have. One thing that is bothering me is that every house I've ever done had a main 4" stack at the very end of the run. Since the end of this run is only 2" that doesn't seem appropriate. This is also a concrete house so I'm trying to run all vents through the interior partition walls since those will be wood. Thank you in advance and have a great weekend.

 

[Breplum]

1. I have been brought in after so many DIY attempts at slab plumbing that was botched I lost count. I do not recommend executing the slab without professional looking over your shoulder
2. You don't need 4" in your case. 3" is plenty.
3. full size cleanout on end of run (again, 3" is fine) and 4" cleanout when you exit, heading toward septic if you run 4" to septic. 3" run to septic can be fine, but a lot of jurisdictions want 4"
4.NEVER use double wye in horizontal run...it is only for verticals. one 3 x 2 combo (or 4 x 2) for each fixture so yu can get slope proper.
5. Total vent area must equal vent area of minimum 3", which is total vent area min. of 7.065" (that's code, will less work?, likely, I've seen engineers argue that point.)
There is no such thing as a combo tee, there are only combo WYE.
Toilet only needs and performs just fine with 3"
For vents, combo on it's back is the fitting to use
Washer only needs 2" drain, 1.5" vent

Soil settlement and lack of true, proper compaction is a primary failure point for DIY. Alignment failure during pour and backfill is second main weakness.

If you do PEX in the slab for water, use SCH 80 PVC electrical sweeps and stubs to prevent concrete contact with PEX...and protect all pipe from contact with concrete in all risers.
Anchor the stainless steel closet bend with upside down brass, long closet bolts (bent on the ends) held in place with s.s. or brass nuts.
HIRE A PRO BEFORE YOU EVEN THINK ABOUT CEMENTING WITH SOLVENT GLUE

 

[Sponsor]

 

[DFisher15]

1. I have been brought in after so many DIY attempts at slab plumbing that was botched I lost count. I do not recommend executing the slab without professional looking over your shoulder
2. You don't need 4" in your case. 3" is plenty.
3. full size cleanout on end of run (again, 3" is fine) and 4" cleanout when you exit, heading toward septic if you run 4" to septic. 3" run to septic can be fine, but a lot of jurisdictions want 4"
4.NEVER use double wye in horizontal run...it is only for verticals. one 3 x 2 combo (or 4 x 2) for each fixture so yu can get slope proper.
5. Total vent area must equal vent area of minimum 3", which is total vent area min. of 7.065" (that's code, will less work?, likely, I've seen engineers argue that point.)
There is no such thing as a combo tee, there are only combo WYE.
Toilet only needs and performs just fine with 3"
For vents, combo on it's back is the fitting to use
Washer only needs 2" drain, 1.5" vent

Soil settlement and lack of true, proper compaction is a primary failure point for DIY. Alignment failure during pour and backfill is second main weakness.

If you do PEX in the slab for water, use SCH 80 PVC electrical sweeps and stubs to prevent concrete contact with PEX...and protect all pipe from contact with concrete in all risers.
Anchor the stainless steel closet bend with upside down brass, long closet bolts (bent on the ends) held in place with s.s. or brass nuts.
HIRE A PRO BEFORE YOU EVEN THINK ABOUT CEMENTING WITH SOLVENT GLUE

Thank you for the response, this is very helpful. I'm a mechanical contractor and have been glueing 1/2"-12" PVC for 15+ years so placement and assembly is not problem, the DWV stuff is where I get lost because I generally work with pressure systems and schedule 80. Am I hearing you correctly that I can add all my vents together to meet the vent size requirement? So if I need vent area of 7.065, my three 2" vents will not cut it. But I could upsize the laundry vent to be 3" and be within striking distance. Do you recommend I run 3" all the way to the sink or will 2" be OK since that is the only thing feeding it? Thank you again!

 

[Breplum]

The area of vents is what the code is referring to.
A 2" vent has an area of 3.14 sq. in. so two 2" and a 1-1/2" vent totals 8.03" and you have satisfied the minimum.
You are fine with 2" past the bathroom (with a c.o. at the end of the run). You just would need a 3" c.o. on a wall to service that portion of the house line. Though the thought of bringing in a big sewer machine into the middle of a house isn't ideal so I would do 3" all the way to the kitchen end of the house to have the 3" c.o. outside.