# PVC below slab, no hub above question



## hroark2112 (Apr 16, 2011)

Looked at a project today, as usual they're on a tight budget. I can run PVC under slab but the above ceiling is plenum. 

Simple question. Can I put the PVC to CI fitting just below the top plate or do I have to put it near slab level, below the tapped tee or cleanout tee? The plans also say I can run PEX in the non-plenum space, but I'd rather run copper. 

It's not a ton of $$ but I'd like to show the GC that I'm trying to help his budget.


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## luv2plumb (Apr 30, 2010)

Depends on the fire rating of the wall and what the drawings show....I have done it both ways without an issue. I don't see a problem with it since the wall itself is not part of the plenum


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## skitian (Apr 5, 2011)

I've been told that it depends if the wall sealed. Are they running drywall all the way up to the joists?


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## U666A (Dec 11, 2010)

Any commercial building I've done that have spec'd plastic u/g and nohub above grade, we make the transition just below the u/s of slab, and stub up in cast.


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## Tommy plumber (Feb 19, 2010)

U666A said:


> Any commercial building I've done that have spec'd plastic u/g and nohub above grade, we make the transition just below the u/s of slab, and stub up in cast.


 




That's the way we used to do it too. Don't forget the c.o.'s at the base of the stacks.


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## RealLivePlumber (Jun 22, 2008)

RFI
:yes:


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## hroark2112 (Apr 16, 2011)

U666A said:


> Any commercial building I've done that have spec'd plastic u/g and nohub above grade, we make the transition just below the u/s of slab, and stub up in cast.


Oh crap. That's right.

:wallbash:

I knew that.

Thanks for the slap in the head.


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## SlickRick (Sep 3, 2009)

A lot of the time the transition at slab level in a commercial bldg is to keep the sound down so they can't hear the water draining from upper floors. If the ceiling is return air, you are just concerned about the fire rating, check it out and save the extra money for the CI.


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## U666A (Dec 11, 2010)

SlickRick said:


> A lot of the time the transition at slab level in a commercial bldg is to keep the sound down so they can't hear the water draining from upper floors. If the ceiling is return air, you are just concerned about the fire rating, check it out and save the extra money for the CI.


Correct, but it depends also where the penetrations are. If in any sort of mechanical room, fire rated pipe is neccessary as well.


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## SlickRick (Sep 3, 2009)

U666A said:


> Correct, but it depends also where the penetrations are. If in any sort of mechanical room, fire rated pipe is neccessary as well.


That's what I was saying. Put it where you have too, save the money where you don't.


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## U666A (Dec 11, 2010)

SlickRick said:


> That's what I was saying. Put it where you have too, save the money where you don't.


Agreed.

Like someone stated, RFI.


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## plumber666 (Sep 19, 2010)

U666A said:


> Any commercial building I've done that have spec'd plastic u/g and nohub above grade, we make the transition just below the u/s of slab, and stub up in cast.


We always stub ABS through the floor. High enough for a water test, then after the floors poured cut it back enough for an MJ clamp and go cast from there. Seen inspectors get down on their knees and make sure there was no more than "two fingers" of ABS showing.


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## Plumbus (Aug 4, 2008)

U666A said:


> Correct, but it depends also where the penetrations are. If in any sort of mechanical room, fire rated pipe is necessary as well.


Not just the mechanical room, but any penetration in a fire rated wall would have to be CI, Durham or DWV copper.


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## Miguel (Aug 10, 2009)

Yeh. We're starting a job shortly where they spec'd cast and copper but PVC OK below grade, all for fire rating. We bid based on all transitions below grade which turns out to be good since the fire marshal will not allow any plastic stubs anywhere above the concrete.


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