Q re venting basement bath

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Soke, Apr 13, 2007.

  1. Soke

    Soke New Member

    Messages:
    8
    I am installing a basement bathroom and want to make sure I properly vent. I need to tap into a 4" drainpipe that runs across the basement floor. This pipe provides drainage to a 1/2 bath on first floor, and runs across basement floor to the main stack that drains upstairs bathrooms and kitchen, and vents out to the roof. The bathroom is to be installed in the corner of the basement where the pipe comes down from the 1/2 bath. This pipe goes to that bath but does not vent out to the roof.

    So, I need to put three Wyes into this 4" inch floor pipe. One 3" Wye that will run to the toilet, one 1.5" or 2" Wye that will run to the sink, and one 2" Wye that will run to the shower drain. Toilet is within 3' of sink, and shower drain is within 8' of sink.

    Given that background, which I hope makes sense, I have been told various things on venting: (1) Given the nature of this floor pipe, which ultimately connects to the house's main vent stack (about 15' away from bathroom location), that I don't need to provide extra venting at all in this basement bath; (2) That I need to pursue much more complicated venting of each drain (toilet, sink, shower); and (3) That I could put one AAV (mini studorvent) in the sink cabinet, on sink drain pipe, and that AAV will provide sufficient venting for the whole bathroom. I like option 1 but it seems too good to be true. I like option 3 as well.

    What do you think of these options? Thank you for any guidance you may have.
    Last edited: Apr 13, 2007
  2. leejosepho

    leejosepho DIY scratch-pad engineer

    My guess is that the vented 4" pipe will accept your new bathroom and work just fine without any additional venting, but I can see how a flush from above at least *might* make the AAV necessary.
  3. Soke

    Soke New Member

    Messages:
    8
    Thank you very much for your reply. I am recovering from a bad contractor who installed Wyes the wrong way and I ended up with sewer from the 1/2 bath all over my basement. I re-dug up the floor, removed his PVC work, and put in a straight line as a quick fix, and now am trying to complete myself. I didn't trust the fact he planned no venting. I will need an inspection from the county but would like to do it right the first time. Thank you again.
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Let's back up minute. You describe the main stack in the corner as the pipe bringing the waste down from the upper floors. If so, that is not a vent stack. The portion of it way up above which goes to the roof is a vent, but the lower portion carrying waste is not a vent. It sounds like you have NO vent down there, and that is definitely not acceptable.

    Air admittance valves might be accepted in your jurisdiction, but are an invitation to an ugly mess if you have a main backup and the studor leaks.
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    I believe what he has described is a 4" line across the basement floor, with its beginning end receiving waste from the half-bath above the proposed new basement bath, and with the pipe's other end being vented out through the roof while receiving waste from the kitchen and main bath above its outlet.

    So then, and assuming the half-bath has no plumbing problems, the question is whether a new bath directly below it in series would have/cause any new problem.
    Last edited: Apr 14, 2007
  6. leejosepho

    leejosepho DIY scratch-pad engineer

    Were that bath and the wyes originally installed together, or was something later changed or added?
  7. Soke

    Soke New Member

    Messages:
    8
    Thank you all for your help. I need to run to kids' soccer games but will come back later today. Leejospeph is correct in his description, this will be under the 1/2 bath. Basement bath is new, being installed into original cast iron piping that runs across basement floor. Thanks again.
  8. markts30

    markts30 Commercial Plumber

    Messages:
    630
    Location:
    Phoenix, AZ
    1st - you will have to have some sort of venting in the new bath...
    You cannot rely on either of the lines going to the upper floors for venting as they are waste lines...
    That would leave either studor-type vents or (preferably) actual venting lines that would tie into the upper floor vents before exiting the roof....
    The min size you could use for the vents is 2" - that would be sufficient if you could tie all the bsmt vents together and just run it up to the vent tie in...
  9. Soke

    Soke New Member

    Messages:
    8
    Thanks everyone. I double checked and the 1/2 bath on the first floor, under which the basement bath is to be installed, does have a 2" vent pipe out through the roof. I was incorrect in my first posting.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,636
    Location:
    Cave Creek, Arizona
    venting

    #1 is totally incorrect
    #2 is the ideal
    #3 may be an option DEPENDING on exactly how the piping is installed. What you describe, how we interpret it, our suggestions, and how you actually install the piping could be vastly different.
  11. leejosepho

    leejosepho DIY scratch-pad engineer

    How did you end up with sewage on the basement floor? Had something that had been roughed-in later back up and leak?
  12. Soke

    Soke New Member

    Messages:
    8
    We hired a contractor to do the bath. He was incompetent. If the below picture comes through you can see how he plumbed it in -- note that the water/sewer from upstairs runs from top of picture to bottom. He did this and cemented over it. The next day (a Saturday), while my wife and I were wondering how the inspector would judge things, we went downstairs and found the mess on the floor. He plumbed in two Wyes backwards so the sewer/water just flowed right out. (Turns out he of course never applied for an inspection as we had asked.) I dug it out and found it as the picture shows.

    [​IMG]

    (There was also a clog dowstream I had to snake out)
    Last edited: Apr 14, 2007
  13. Soke

    Soke New Member

    Messages:
    8
    Thanks. If you can view the picture below you can see how the line runs (this is what I removed and have to redo). But I will have to install sink wye first, then toilet almost adjacent (I would not do the 90 degree anlge he has but run toilet line straight into the wye), then finally the wye for the shower a few feet downstream. Thanks for your help

    [​IMG]
    Last edited: Apr 14, 2007
  14. leejosepho

    leejosepho DIY scratch-pad engineer

    I do not always do things "by the book" when I am quite sure they will work in spite of my deviation, but even I would not do what you are planning without first finding out precisely what fittings are actually proper, how they should be ordered and oriented, and how to add some venting.
  15. i like the way that was said.

    You do have to use San-T fittings for sinks, for example, and I notice the thread originator said "Wye" in the quoted text.

    Soke, there could be more places where we can help but you may be moving too fast, describing too breezily. Take it one small step at a time.

    david
  16. leejosepho

    leejosepho DIY scratch-pad engineer

    Seeing that picture of the basement mess reminded me of a past situation where a garage had been converted into a family room with a bathroom. That second bath was at ground level, and the main floor of the house sat up about two feet ... and one afternoon I stepped down into that room to discover sewage and wash water from above all over the floor. The septic system had backed up, and nothing from anywhere had any lower place to go.

    The initial question here was about plumbing/venting a new bath in series with an existing one, but the real issue here has turned out to be about that same kind of flood almost certainly happening again no matter what fittings are turned which way. My own best guess is that the basement bath needs to be drained into a sump and pumped out in order to avoid compromising the integrity of the remainder of the system as it first was.
  17. leejosepho

    leejosepho DIY scratch-pad engineer

    Are horizontal drain-check valves ever used in this kind of situation? I can imagine problems with a check-flapper in a toilet line ...
  18. Soke

    Soke New Member

    Messages:
    8
    Q re basement bath venting and etc.

    Thanks again everyone for your comments. I am starting to think that, once I get my money back from the first guy (or even if not), I should hire a good plumber to do the rough in. Another sewer flood is not very appealing. Problem is that here were I live (Northern VA), my phone calls aren't returned for such a small job because there are lots of bigger and easier projects all around for folks to work on. Even with the housing prices stalling and falling, the amount of new construction continuing on is amazing to me. Maybe if I say the floor is already smashed out people will think it won't be so bad.
  19. leejosepho

    leejosepho DIY scratch-pad engineer

    Your efforts so far easily cause me to believe you are willing and able to do the work yourself, and there are folks here who "answer the phone" quite willingly and who both can and will help you be sure things are done properly.
  20. Soke

    Soke New Member

    Messages:
    8
    Thanks on Q re venting

    Thank you all for your help and encouragement. I will do some more research, and planning, and will likely come back soon with some more questions or to seek comments on a more specific plan. Thanks again.
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