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-   -   question about vent stack (http://www.diychatroom.com/f7/question-about-vent-stack-144533/)

firstimereno 05-22-2012 02:54 PM

question about vent stack
 
hello -

i have a washing machine drain line that exits bottom of wall and runs downhill between (2) 2x10 floor joists before it connects to main 3".

i need to add a 1.5" vent stack in an adjacent wall in laundry, up thru roof or with aav in attic. here's problem... the 2" laundry drain line doesn't get below the joists until the very end, which is dead under my den.

i can't branch off the down-drop below washer box in wall, b/c the hot and cold lines are on either side of the drain line.

i wanted to branch off the 2" in crawlspace with a 2x2x1.5" sanitary tee, and go over about 12" (to the other side of joist) and up thru that adjacent wall... how can i do this without cutting/boring thru floor joist? i really would prefer not to to that. i also don't want to cut out section/header, etc. messing with the already testy floor situation i have would not be good idea. please help!!!

also one more question... (i'm speaking in direction of heading from fixture toward septic) is it better to put vent line after the trap or before? the trap is right after my 90 under floor/wall, and this whole line only serves the washing machine. vent uphill of trap or after trap? just want to make sure.

thanks for any help.

ben's plumbing 05-22-2012 08:27 PM

Quote:

Originally Posted by firstimereno (Post 926528)
hello -

i have a washing machine drain line that exits bottom of wall and runs downhill between (2) 2x10 floor joists before it connects to main 3".

i need to add a 1.5" vent stack in an adjacent wall in laundry, up thru roof or with aav in attic. here's problem... the 2" laundry drain line doesn't get below the joists until the very end, which is dead under my den.

i can't branch off the down-drop below washer box in wall, b/c the hot and cold lines are on either side of the drain line.

i wanted to branch off the 2" in crawlspace with a 2x2x1.5" sanitary tee, and go over about 12" (to the other side of joist) and up thru that adjacent wall... how can i do this without cutting/boring thru floor joist? i really would prefer not to to that. i also don't want to cut out section/header, etc. messing with the already testy floor situation i have would not be good idea. please help!!!

also one more question... (i'm speaking in direction of heading from fixture toward septic) is it better to put vent line after the trap or before? the trap is right after my 90 under floor/wall, and this whole line only serves the washing machine. vent uphill of trap or after trap? just want to make sure.

thanks for any help.

show us a picture if you can.....how far away from 3" main stack are you...

jaydevries 05-22-2012 08:37 PM

here is a link with a common wash machine rough in. hope fully this will help. it is also code that trap is on same floor as wash machine. also how far away is 3"
http://www.pbase.com/image/74640075

ben's plumbing 05-22-2012 10:26 PM

hello anybody outthere.......ding dong..:eek:

firstimereno 05-22-2012 10:38 PM

jay: pretty sure your picture link shows a "S" trap, which is a no-no.

ben: scratch prev question. jay mentioned something that poses another question i have. he mentioned trap has to be on same floor as fixture. i can't squeeze trap in wall cavity, it has to go under floor. (the old one was under floor just like my new one, since 1988. no problems, never stunk or clogged.) sure hope you agree trap can stay in crawlspace, after my 90 at base of vert drop.

new question is... i have looked everywhere, but can't find any info on this... on my new setup, my AAV and the 2x2x1.5 Y that supplies it is in the wall cavity, just below the washer connection box, which puts it before the trap. will having the AAV before the trap pose any problems, such as siphoning? or is siphoning just a problem when trap too close to a main drain, etc? thanks for the help, hope y'all are still on the cpu tonight....

ben's plumbing 05-22-2012 10:46 PM

still need to know how far away 3" stack is????

jaydevries 05-22-2012 11:01 PM

here you are not allowed to use an aav on wash machine. that is a passable wash machine pic including the p trap. some inspector here like to see more length of pipe between trap and t though. here is a pic of s trap in link
also as long as horizontal is a 3"
http://www.toolstation.com/shop/Plum.../sd2907/p19250

firstimereno 05-22-2012 11:47 PM

jay: yep, that's what i was thinking about when i wrote that. i keep reading that trap and vent line need to be at least 2 pipe widths apart.

ben: sorry about that. the trap is approx 9-10' from the 3" main. the AAV will end up being about 6.5' up on the same wall as washer box, about 34" above the washer box. setting washer box at about 46" off top layer of subfloor. the 2x2x1.5 Y will be about halfway (vertically) between box and floor. (worried the vent before trap will cause some sort of siphoning)

btw... i'm in Alabama, in unincorporated rural county. no local codes here. but i sure don't want any siphoning. and the washer drain has worked fine since 1988 without its own vent... i just wanted to add to reduce the gurgle sound and impress the next owner's inspector, as i plan to sell within 10 yrs. (it has always gurgled at the peak of draining after the wash cycle, but has never overflowed or backed up while draining.

(i want to go above/beyond, and make it right. but if i have to create some sort of crazy loop system, or add 30' of pipe to route a complete thru-roof vent, then i'll scrap the whole thing and continue with no vent!)


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