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Thread: p trap plumbing question. pic included.

  1. #16
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    Quote Originally Posted by Tom Sawyer View Post
    No vent is not vent. That stack serves the fixtures below it. If you use it the way you are trying to use it, you would need to re-vent all the lower fixtures to a point above the flood level rim of the 2nd story fixtures. In short, you can't tie into that 3" pipe with waste water. You need to run a separate 3" pipe all the way to probably the basement and tie into the waste there. Absolutely do not continue to do what you are doing or you will have big problems.
    Quote Originally Posted by wjcandee View Post
    Uh-boy. Dude, study this for some help. http://www.co.lincoln.or.us/planning...mbingguide.pdf Then, look at p. 9 where there is a picture of a correctly-vented tub p-trap.

    Also, p.3 of this guide may be helpful to you: http://www.klickitatcounty.org/build...andout0411.pdf Also look at p.6, and p.4 and 5.

    Thank you for the links and thank you for taking the time to educate such a novice like me. One thing I'm trying to understand is if this is such a big no-no, then how was the old tub draining into this stack without causing problems? I'd assume the builder of this townhouse would've needed to build it all to code, albeit 20 yrs ago. By no means I'm saying you guys are wrong, but maybe with my limited knowledge, I'm not explaining things correctly.

    Btw, only fixtures on first floor is a toilet, bathroom sink and kitchen sink.

  2. #17
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    I just went up to the attic to check how everything is vented, and this 3" pipe is the main vent stack. But from this pipe, there is a 2" vent offshoot going into the second bath. The kitchen and downstairs half bath are below the second bath. So maybe the 2" vent is venting both second bath as well as downstairs. The reason i think that is true is because all three old fixtures in master bath (the one I'm renovating) were plumbed to drain into this 3" pipe, as seen below. First connection is for toilet, second for sink (sink has separate vent), and third (bottom of pic) is for old tub. Builder wouldn't have drained toilet into vent stack for downstairs fixtures.

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    Last edited by aharami; 12-21-2013 at 09:08 AM.

  3. #18
    Master Plumber Caduceus's Avatar
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    It's okay to pipe the shower into the stack. That is the main soil stack and fixtures can drain into it as long as they have their own independent vent. Any fixtures connecting to the stack below should already have their own vents.
    If that 3"x3"x2" wye is the highest connected fixture, then the remainder of the soil stack becomes the stack vent and will also serve as the vent for the 2" shower p-trap. Meaning this...it looks like upstream of the shower the 3" 90 bends vertically and may go through the roof from there. As long as no fixtures flow in from another higher level than the shower.

  4. #19
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    Quote Originally Posted by Caduceus View Post
    It's okay to pipe the shower into the stack. That is the main soil stack and fixtures can drain into it as long as they have their own independent vent. Any fixtures connecting to the stack below should already have their own vents.
    If that 3"x3"x2" wye is the highest connected fixture, then the remainder of the soil stack becomes the stack vent and will also serve as the vent for the 2" shower p-trap. Meaning this...it looks like upstream of the shower the 3" 90 bends vertically and may go through the roof from there. As long as no fixtures flow in from another higher level than the shower.
    Yes, that's right, no other fixture upstream of the shower wye. Thank you for explaining.

    Now the question is: can I take the shower ptrap left to right and then make a u into the 3"main using a 3x3x2 wye? See picture
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  5. #20
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    Also, I'm assuming I did this incorrectly, right? Since the drain on the left goes down before hitting the vent, it would be considered an s trap. I'd need to take out that 90 degree turn and put in a T, and then connect to the main vent in the attic, right?

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  6. #21
    Forum Admin, Expert Plumber Terry's Avatar
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    Extend up, add a santee and then revent at 42" to the other vent.
    Going from vertical to horizontal requires a long turn 90 el.
    The vents can use med 90's or vent 90's
    Medium 90's cost less then a true vent 90, so I mainly carry and use the medium in those locations.

  7. #22
    Master Plumber Caduceus's Avatar
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    Quote Originally Posted by aharami View Post
    Yes, that's right, no other fixture upstream of the shower wye. Thank you for explaining.

    Now the question is: can I take the shower ptrap left to right and then make a u into the 3"main using a 3x3x2 wye? See picture
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    As long as the wye is laying down as seen in the photo above, but you may run out of room using the approved fittings. Tilting the wye above the drain or ofsetting down into the wye would require a new vent to avoid s-trapping. It's not allowed for 90s to be installed horizontally on drainage, so 45 degree bends will have to be used to make 90 bends. Some codes also do not allow a 135 degree bend for a fixture drain. It seems that you're trying to get the drain on center of the shower for a nice appearance, but is there any way to adjust the design so that the trap can flow more directly into the 3"?

  8. #23
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    I just went up to the attic to check how everything is vented, and this 3" pipe is the main vent stack. But from this pipe, there is a 2" vent offshoot going into the second bath. The kitchen and downstairs half bath are below the second bath. So maybe the 2" vent is venting both second bath as well as downstairs.
    So you're thinking that the other bathrooms are vented by a 2" up past this floor, and tied in at the attic?
    The 3" you are tying into for the shower is used for waste on the downside of the wye, all the way down and ties in downstream of of the other fixtures?
    That makes more sense.

  9. #24
    Moderator & Master Plumber hj's Avatar
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    quote; What you are trying to do is to pipe a fixture into the house stack. You can't do that.

    And why not, since it appears he already has TWO existing drains connected to it. As for the original question, if you run the drain horizontal as necessary to avoid a separate vent, the "P" trap will probably have to hang through the ceiling. IF it would work then a "combo" in the 3" line and a pipe to the "P" trap should work perfectly. You would rotate the P trap's "J" bend to line up with the shower drain location.
    Last edited by hj; 12-21-2013 at 02:24 PM.
    Licensed residential and commercial plumber

  10. #25
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    I want to say that this thread has been very educational. Thank you to everyone who participated and helped me out. I have decided to re-plumb everything and connect the sink pipe to the toilet pipe thus eliminating the wye that was getting in my way before and connect the shower ptrap properly to the main stack without doing any uturns or funky stuff.

    This thread made me realize that the toilet wasn't vented properly. 3" arm after flange was going down before meeting vent. So I'm going to create a vent via a 3x3x1.5 sanitee and connecting across the joists as shown below.
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    But I have one question. Does a vent pipe always have to have a pitch like drain pipes, or can a portion of a 1.5" pipe flow downward to meet the main vent stack?

    Would something like this be legal for venting?
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  11. #26
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    Table 906.1
    Maximum Distance of Fixture Trap from Vent
    Size of Trap
    (inches)
    Slope
    (inch per foot)
    Distance From Trap
    (feet)
    1 1/4
    1/4
    5
    1 1/2
    1/4
    6
    2
    1/4
    8
    3
    1/8
    12
    4
    1/8
    16

    Your shower drain needs to be routed so that you can get a vertical vent riser in a wall within 8 feet of the trap. No part of a trap arm from the trap to the vent riser can exceed 1/4" per foot of fall, or the vent will be broken.

    Vertical vents below the flood rim of the fixtures are never ok..


    Last edited by cacher_chick; 12-21-2013 at 07:30 PM.

  12. #27
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    Trap-to-vent distance is determined by how close the horizontal drain connection is to the vent connection in relation to the trap. Where the vertical riser is has no bearing on the 8 ft. limitation. For example; The 3"x3"x2" wye going off to the shower looks like it will have a trap to vent distance of about 18"-24". The vent starts at the connection of the wye. Additionally, the toilet is vented through the soil stack. Even with an offset on the drain before the connection to the stack, this is allowable by most codes for toilets only as long as another toilet isn't connected upstream....which there isn't.
    If you did add a vent for the toilet, 2" is code. I understand that it would be difficult with larger fittings to get it done, but because the toilet is stack venting it's a moot point anyways. An additional 1 1/2" vent on a DIY project couldn't do any harm as long as it isn't looped over with 90s as shown in your picture. A horizontal vent must always continue with slope/fall as cacher_chick mentioned and then go vertical to allow condensation to drain or wastewater in the event of a clog.
    Last edited by Caduceus; 12-22-2013 at 06:14 AM.

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