Slab plumbing with little clearance

[japerry]

Getting close to laying a slab, but I need some advice that I haven't been able to find 100% answer for. For some background:

http://www.garagejournal.com/forum/showthread.php?t=204177

One of the problems that started out was that our sewer line is only 20" below grade. That meant 4" tube would be required. (only need 1/8" rise!)

https://scontent-b.**.fbcdn.net/hphotos-frc3/1380751_815011279150_1167877532_n.jpg

Its also 74' from the entrance to the garage.
https://scontent-b.**.fbcdn.net/hphotos-prn2/1385430_815011368970_1335484362_n.jpg

Luckily the garage is above grade, where the 6" of gravel is actually above grade. that gives me 26" from bottom of concrete.

74' * 1/8" rise = 9.25" from sewer line to entrance to the garage.

So from the base to the garage I have about 16.75" to work with. However, since the grade slopes down a little, I really only have about 12" to work with.

My question comes down to this, can I run vents vertically from the mainline according to this photo? Each has a vent, but the shower and WC vents will have water flowing through them potentially...

Also, what are the rules about running a 1/2" PEX line across ABS pipe under a slab? I keep seeing rules saying you must space them out if you're using unapproved materials under a grade... but I thought both PEX and ABS are approved?

 

[japerry]

So a little update, it looks like this cannot be done. Going in for round two tonight to see if I can get it straightened out.

 

[bfarroo]

I'm in the process of getting my plumbing set also. In the pictures aren't your vents going to go up through a wall and out the top of the building? How would water flow through them or are you planning on keeping the vents below grade? My plan will be laid out similar to yours and there will be an interior wall just to the right of your plumbing. Each vent will go up through the interior wall, come together and exit the building.

 

[larry4406]

Run your plumbing at 1/4 inch per foot of fall. For the toilet, it's center should be 13 inches off the finished rear wall. Make sure your toilet will net 15 inches side to side clearance minimum with walls, vanities, etc (work to finished dimensions, not rough framing).

On the toilet rough in, they make an adapter that converts 3 inches to 4 inches. The 4 inch will be vertical and come up thru your floor. Run the 4 inch high relative to the floor and cap it with a test cap. Later, after the concrete is poured and your finished floor is installed (vinyl, ceramic, etc), you will cut the 4" riser flush with the fininished floor and your closet flange (toilet flange) will then slip into the 4" inch pipe for gluing (you will need to radius the inside of the 4" to receive the closet flange, the closet flange will then sit flush to the finished surface). A 3" inch riser is a POA since the hub on the closet flange would then have to slip over the pipe making you chip the concrete out.

Regarding venting, your sink should tee/wye into the toilet line, rise vertically with a stub out for your vanity, and then continue rising to the vent. Hope attached picture of my ground works rough-in helps you.

 

[bfarroo]

I see some rough ins where there is a box framed out around one of the pipes. What is the purpose of this? is this for a bathtub?

 

[bfarroo]

Looking at the picture in post 4 my main sewer line will extend from right to left and will be 3 inch. The toilet will be y'd into the main line the appropriate distance from the wall. The main line will 90 and go up the left wall as the main stack. Now here's one of my questions. Instead of y'ing in the sink and urinal into the main sewer line could they be connected into the main stack going up the wall directly.( the drain lines would go across the wall inside the studs) They would be less than 5 feet from the main stack on either side. I don't think I will need a vent for the sink/urinal in this scenario would I? Also with the above picture how does the venting for the shower work? It seems like the vent is quite a ways from the shower.

 

[mygarageone]

You don't need 1/4" per ft , min code requires is 1/8" per ft. At 100 ft that a bunch of saved drop.
I can not tell from your pic.s but you do not need 4" inside the garage . But when you change from 4" to 3" you should have a full size 4" C.O . You are not allow to have a tee on it's back unless you are crown venting and that's become a no, no also. The shower doesn't have to be vented if it's 3o" down stream of the toilet , besides the vent you show would serve no purpose., no does the one for the toilet. at the upstream end of your main , you should have the vent , it can have a couple of fixtures draining into the vertical portion of the vent.

I guess The real question is are you pulling a permit ? if so , call your plumbing inspector and he will I am sure assist you with a proper lay out. If not , anything is allowed . Not really but no inspection no issues. Having said that you really need to do it right and not have issues down the road,
Looking closer you do have 3" inside the garage. But you only need 1/8" per ft drop on anything including the 4" you ran to the garage.

 

[mygarageone]

Ya know some times , if ask a plumber for a code approved design , he will do it for a small fee , certainly worth looking into. I have done that for yrs.