Took your advice - need some opinions

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Alex S, Aug 23, 2021.

  1. Alex S

    Alex S New Member

    Joined:
    Jan 9, 2019
    Location:
    Houston, TX
    Hey all,

    A few months back I posted about my shower drain rerouting. Essentially I needed to get a drain into the middle of a 5x6 walk in shower but needed to sort out venting. You suggested running it to the wall and then back towards the drain. This method was accepted and the attached was mocked up.

    Forgive the pile of 22.5 deg bends on the vent that was me just seeing what it would take to get it vertical.

    Seems OK but I have two concerns;

    1. Putting a level on the slope of the drain on both of the two runs is more than 1/2 " per foot. Does aggressive slope cause any issues? I don't think this slope is going to siphon the p-trap so im not too worried about that?

    2. The vent isn't running horizontal below the slab, but its not vertical either. If I had to guess the piece of vent pipe before reaching the wall its running at about 30 degrees.

    Any comments would be appreciated here to save me time with the plumber as I am trying to do all the digging / hammering so that I don't waste his time doing excavation or demo. None of this is glued or secured.

    The overview pic attached should help explain - there are some other ones of different viewpoints I uploaded also.

    You guys are amazing and I really appreciate the fact people take the time to look at posts and comment.
     

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  2. John Gayewski

    John Gayewski In the Trades

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    Aug 7, 2021
    Location:
    Iowa
    I think i would have drained the shower trap arm into a tee. Then from the bottom of the tee back to the drain. This would allow you to put a cleanout in the wall and clean the portion of the drain that goes from the tee to your new connection.
     

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  4. wwhitney

    wwhitney Well-Known Member

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    Location:
    Berkeley, CA
    1/2" per foot isn't an issue in and of itself. But the total drop from the trap outlet to the vent take off is limited to one inside pipe diameter. So if that's 2" pipe, have you confirmed that the total fall is less than 2"?

    As question (2), the horizontal vent run certainly looks fairly flat. You're supposed to arrange for the san-tee on its back (or wye) to be located so that the vent can stay at most 45 degrees off plumb while staying under the slab. I assume you are under the IPC; a san-tee on its back isn't allowed under the UPC.

    John's suggestion is a good one if you have enough height available for that short vertical segment. To minimize the height required, you could rotate the san-tee 45 degrees around the inlet from true vertical. E.g. point the trap arm perpendicular to the wall; hit a horizontal LT90 to be briefly parallel to the wall; then hit the tilted san-tee, so that your vent takeoff is 45 degrees off plumb pointed towards the wall, and the drain can turn horizontal again with a street 45.

    Cheers, Wayne
     
  5. Alex S

    Alex S New Member

    Joined:
    Jan 9, 2019
    Location:
    Houston, TX
    Hey guys I really appreciate the feedback. I tend to agree that a cleanout would be a good idea - but I'm not sure how to accomplish John's drawing and keep to code with trap arm visibility to vent. Any chance you could better explain the pieces we are talking about?

    Say that the trap arm is going to run into the wall as it currently is, but instead of the vent coming up the top you are saying to use a wye at the bend not before? The reason the vent is before the turn is because I was under the impression the trap arm was required to "see" or have line of sight to the vent. The vent being at the bend would prevent line of sight - or do I misinterpret the IPC here?
     
  6. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    I'm aware of no such requirement. Not a problem to have a horizontal elbow in the trap arm, done all the time with sinks. Some codes (UPC?) require a cleanout in the trap arm if the total degrees of horizontal bend exceed a certain threshold, but that would be above 90 degrees.

    The rules as I understand are that the vent has to come off before or as the trap arm meets another drain, and that the trap arm can fall no more than one pipe diameter before the vent takeoff occurs, while still falling at least 1/4" per foot.


    Cheers, Wayne
     
  7. Alex S

    Alex S New Member

    Joined:
    Jan 9, 2019
    Location:
    Houston, TX
    Thanks Wayne, to be honest I have no idea when I picked up this line of sight requirement assumption from trap arm to vent- I have just always thought it to be true and its never been a factor until now. Totally understand the pipe diameter being max fall before vent - that has always made sense to me. The line of sight didn't really ever make sense to me - just something I have adopted. I suppose I could launch the vent from the apex of the bend if thats the case - I would get the vent more direct/in line with the trap arm (able to be used as a clean out) - I would lose line of sight from the trap arm to the vent - but I guess that's not an issue. I will try and find where I picked that up from - now I am questioning everything haha.
     
  8. GatorHawk

    GatorHawk New Member

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    Aug 13, 2021
    Location:
    Alabama
    I'm not a plumber, so there might be flaws in my sketch, but could you do something like the sketch below to simplify the layout? (Blue = drain line; Orange = fittings; Green = vent)

    I don't know if you have the depth, but you could rotate a combo wye up 45 degrees then use a 45 to turn it vertically at the wall for your vent. Since you are running at 1/2 inch per foot, you could dig a little deeper to get 1/4 per foot slope and gain a little depth for the vent. The shallower slope also allows you to increase the length of the trap arm between the drain and vent.

    Also, I recommend using sch40 instead of that Fernco 90 to make the final turn, then use a Fernco coupler (the purple blob in the sketch) to connect the two pieces of straight pipe.

    overview.jpg
     
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  9. wwhitney

    wwhitney Well-Known Member

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  10. Alex S

    Alex S New Member

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    Jan 9, 2019
    Location:
    Houston, TX
    That's a super helpful diagram - appreciate you Gator. With a 45deg vent launch from the drain pipe for every inch I am away from the wall I will need to travel upwards the same amount. That center drain is 36" off the wall we are travelling to. Even digging down to 1/4" per foot I doubt I will have the height to be as aggressively off the wall as your image suggests - but I think I should try and duplicate this (same thing Wayne is saying) as far off the wall as the vent height run allows. Agreed the rubber 90 will need to get swapped for PVC Sch40 and use the hub couplers that are sub grade approved. Damn ABS house.

    Let me try another example run here. Would you make the WYE 2x2x2 or can I keep 2x2x1.5 for a clean out? Never found a 1.5" clean out - but I guess it would work?
     
  11. Alex S

    Alex S New Member

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    Jan 9, 2019
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    Houston, TX
    Alright - is this what was meant by the above? I think this is a lot cleaner - the slope is fixed to accommodate a steeper vent run to the wall and the 1.5" vent can get a cleanout on it so we can get down to that new run should it be needed ever.

    Switched over to the hub coupler for ABS to PVC that is rated for below ground, ditched the fernpro quick 90.

    Just wanted to quickly mock up what I thought you were intending in the above for comment. Thanks fellas!
     

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  12. John Gayewski

    John Gayewski In the Trades

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    Aug 7, 2021
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    Iowa
    That's not what I meant, but it will let you put a cleanout in the wall and does look better.
     
  13. Alex S

    Alex S New Member

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    Jan 9, 2019
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    Houston, TX
    A step in the right direction then - I think we are almost there. Hopefully I can hear the opinions of Wayne and Gator and converge on a final solution here haha. It sure is easy to scroll past stuff on the internet so I am hugely grateful to those that are taking time out to comment here - thanks a million.
     
  14. wwhitney

    wwhitney Well-Known Member

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    Mar 17, 2019
    Location:
    Berkeley, CA
    I don't see any problem with the layout, assuming proper slope and total fall before the vent wye. And for getting the vent to that location, I don't have any better suggestions. Maybe John's idea is somewhat better but it does require more total fall from trap to ABS stub.

    Cheers, Wayne
     
  15. Mr tee

    Mr tee In the Trades

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    May 3, 2020
    Location:
    Montana
    Lose that rubber elbow, besides not being approved they are lousy. If a snake goes through it and you have a leak under the slab you will not be happy.
     
  16. Alex S

    Alex S New Member

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    Jan 9, 2019
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    Houston, TX
    Appreciate you Wayne! Thanks for everything sir.
     
  17. Alex S

    Alex S New Member

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    Jan 9, 2019
    Location:
    Houston, TX
    Understood - see the second set of pics above - already gone - just needed a rubber coupler to go from PVC to ABS - 90 rubber is out! Thanks for the eye though.
     
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