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Thread: Question for Terry re: his infamous Graphic

  1. #1
    DIY Junior Member fishbum's Avatar
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    Default Question for Terry re: his infamous Graphic

    I've been sudying this graphic that you always post - on the far left the first floor tub vent goes all the way to the second floor revent.

    Why is that? Does it have to be that way or are you just showing another option?
    Thanks,
    Brian
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  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    If the wall was thick enough to cross behind the 3" stack for the toilet, then it could have revented at 42".

    However, most walls are either 2x4 or 2x6, which is not enough space.
    Therefore the revent, which can only tie in at 42" above a floor, (at least 6" above the flood level of a fixture) must go to the next floor.

    This diagram is standard plumbing in apartments and homes.

    For every pipe going down, you also have one going up.
    Look at the neighbors home and count how many vents are on the roof.
    I normally run between three and eight vents through a roof.
    Last edited by Terry; 10-18-2009 at 11:06 AM.

  3. #3
    DIY Junior Member fishbum's Avatar
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    Thanks, I'm remodeling, adding a second story and gutting the first floor, so I have the "luxury" of removing all DWV piping and redoing everything properly. I'm still working on my plan, which involves lots of routing among floor trusses, wet walls, and around the chimney.
    The only thing that will be original is the cast 3" main waste line and cast vent thru the first floor. Everything else will be new PVC. So I'm reading what I can here and verifying questions with my local CEO before I proceed. I only want to do this once and do it right the first time!
    Brian

  4. #4

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    Yes, you can run in the floor joist, if it runs that way, or create a bulk-head (soffit) to run them in as well...

    Also, if you're gutting the first floor, I'd get rid of the cast iron and replace it all. You've gone that far... don't leave that old stuff in there. It's a pain to tie into the cast iron with the no-hubs every spot you need to. Plus, if the cast iron is looking thin in spots, or has leaky spigots, this is the time to do it, while the walls are open. I ripped mine out from basement to roof: rent a chain cutter, only takes a few hours if you already have it exposed. It will make the rest of the job so much easier...

  5. #5
    DIY Junior Member fishbum's Avatar
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    Well the only remaining cast hub is embedded in a block wall and exits my crawl space for the septic system, so removing that last portion involves digging outside. Oh yeah, and it goes under my garage floor first....

    So I think I can live with one surviving cast hub considering the alternatives!!!

  6. #6

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    If it's hidden and untouched, than yeah. If you've gutted the first floor, and adding a second, won't you have to connect into the stack and vent in the first floor? That's the part I'd replace.

  7. #7
    DIY Junior Member fishbum's Avatar
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    The cast hub (that enters the exterior wall) already has some PVC drain pipe entering it the previous owner added. So I need to remove all the old PVC and re-do it and connect it to the cast hub again. The pvc needs to be redone to accomodate the stack coming down from the second floor.

    I've cut the vertical vent off, it used to project thru the roof, now it stops between floors and i need to route it thru the new floor trusses horizontally about 8 feet before going vertical again up thru a 2nd floor wet wall.

    The hub will be a pain, for sure. The vent is easy to reconnect. My preference would be replace it all. Like I'm doing with the crappy copper plumbing job. And the furnace. And the water pump. And baseboard heat routing...! And most other mechanical systems in this house!

    Good thing there is a great water view....!!!!

  8. #8

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    Quote:
    "Therefore the revent, which can only tie in at 42" above a floor, (at least 6" above the flood level of a fixture) must go to the next floor."

    Terry: the Code requires min 6" above the flood level. The 42" you've mentoined is it at least or should be exact. If it is exact what is the rational behind?

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default vent

    It is 6" above the flood level OR 42" whichever is higher. The rational is that even if you have a fixture with a flood level below 36", (which is what makes the 42" level), there would be nothing to prevent you from someday installing a kitchen sink or other fixture that was at 36" and at that time your lower vent would be a problem.

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