Re: Need your opinion on my layout
Posted by GregO on June 11, 2004 at 13:27:16:
In response to Re: Need your opinion on my layout
Dave,

For your own sake, be careful; do not confuse a wet vent with a horizontal run of dwv. A vent needs a "riser" portion (above 45 degrees). This should be something you only want to do once. Get all your ducks in a row and have it done correctly once. Good luck...

: Did a little digging around and it appears we are both right (sort of). The NSPC and IPC allow horizontal wet vents, while the UPC does not. My region follows the NSPC so I think I would be ok with horizontal vent connections (if they are wet vents). I think I still have to change the vent connections for the tub and shower though.

:
: : CEA, Thanks for your input. I understand what you are proposing. I'm not sure if I will have the room to do what you are proposing without running into a joist, but I will check it out. The way I figure, if the drain is under the wall and pushed up against the back joist, then I need a 12" offset for the toilet, plus half the diameter of the toilet drain, is more than 16" (the joist spacing).

: : To follow up on your point about vents coming out horizontally, what about wet vents? I have seen schematics where the vent for the toilet is actually the drain for the lavatory, where both drains connect horizontally, and then the vent comes off the lavatory drain further back. It seems like the wet part of the vent can be horizontal. Is this an exception to the horizontal venting exclusion?

: : :
: : : None of the fixtures shown are properly vented, because all of their vent connections tie into their drain horizontally. A fixture vent must tie into its drain at an angle within 45 degrees of vertical. A vent can't run horizontally at all until it's at least 6" above the flood rim of the highest fixture it serves (usually a lav).

: : : I'd recommend you consult with a plumber at this point for a better layout, but if it were me, I'd probably do the following. Stud out the wall behind the toilet as your wet wall. It looks like you've got enough room in the long dimension that losing 6" isn't going to be a deal-killer. Extend the new 4" stack up into that wall and don't offset over to the roof vent until you're at least 6" above the lav (in the attic would work, too). Vent the shower and toilet with a vertical vents in the wet wall, from the fixture drains to the vent offset above. As long as the fixtures are properly vented, you can tie them into a single 3" drain that runs where you show the horizontal 4" line under the floor, then into the stack with a wye.

: : : The lav will need a fixture vent of its own--even if you could tie its drain into the stack above the point where the other combined drains tie in, the lav is going to be too far from the stack to use the stack for venting.

: : : If it were me, I'd turn the tub around and plumb two walls instead of three; you still have to vent both the lav and tub, but at least they could share a common drain. If you keep the tub where it is, you'll have to make the drain-to-vent connection in or close enough to the wall to tie the vent in vertically.

: : : Hope this helps. Good luck.





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