Feedback on plumbing floor plan layout-advice needed

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Numerick, May 3, 2014.

  1. Numerick

    Numerick New Member

    Messages:
    9
    Location:
    New Hampshire
    So here it goes, been doing some heavy studying for the past week and I will say one thing. Whoever says plumbing is not complicated just does not understand the level of knowledge it requires to do correctly. So, THANK YOU for all the professionals that are willing to offer their two cents to anyone who is asking. Plumbing is so much more than gluing and soldering pipe together as many lay people/homeowners think.

    I have a small one floor cabin (24 x 20) that has a 4' crawl space with plenty of access that I would like to get some advice on as it applies to the UPC. There are only four plumbing fixtures in the dwelling: Kitchen sink, Toilet, Shower stall, & Bathroom vanity.

    Please reference the diagram below.
    • 2" dry vertical vent pipe through roof available +/- 6 feet from soil stack
    • Shower stall P Trap 6 feet from soil stack
    • Toilet flange 28" from soil stack
    • Bath vanity literally on top of soil stack (from above) less than 12" from center of stack
    • Kitchen sink +/-15 from soil stack

    I am seeking advice regarding the venting of the system. From all I can gather, I anticipate the design would pass UPC inspection given:
    • Shower drain PTrap is within 6 feet of soil stack. PTrap is not individually vented
    • Bath vanity is within 12" of soil stack-not independently vented
    • Kitchen sink will have a AAV or Island loop vent (not preferred because of foot vent length)

    Since the Shower & Vanity PTraps are so close to the soil stack, can the soil stack serve as the vent even though it is offset by 6 feet?

    My concern is that the Dry Vertical 2" vent stack is offset by 6' from the 3' soil stack that goes to the septic tank. Can I make this work correctly?

    Please add advice on Proposed Soil stack layout if possible.

    Nothing has been put together yet. Just need to tie everything together correctly so that it works for the next 100 years.

    Thanks again for any input.




    Plumbing floor plan.jpg
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,237
    Location:
    Land of Cheese
    When you have branch drains connected to a stack, only the uppermost connection is vented by the stack (assuming the fixture trap is within the allowed distance to the vent). You can have fixture vents coming back to the stack, but the vent connections must be made at least 6" above the flood rim of the highest fixture, or 42" above that floor (whichever is greater).

    Once there is liquid in a stack, it is no longer a vent, it is a drain.
    Last edited: May 3, 2014
  3. asktom

    asktom Member

    Messages:
    519
    Location:
    Victor, MT
    Under the UPC a vertical wet vet vent would be acceptable on your 3" stack if the toilet connected at the bottom and the other fixtures teed in above it. The maximum length on the 2" trap arm for your shower is 5', but that is measured from the weir (where the water runs out of the trap) to the edge of the vent. It is going to be close. Is there a structural reason you don't vent the kitchen through the roof?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,270
    Location:
    Cave Creek, Arizona
    quote; When you have branch drains connected to a stack, only the uppermost connection is vented by the stack

    That is true as far as it goes, but in many areas, certain lower fixtures can be "wet vented" even though there is a fixture above them. In this case, however, the toilet is the upper fixture, and it can NEVER be used as a wet vent for sinks, showers, or bathtubs connected below it. Unless the lavatory is connected to the "dry vent" it cannot be offset horizontally.
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,068
    Location:
    Maine
    If you are in NH it's IPC and not UPC so, your distance from toilet to vent is unlimited. You can vent two bath groups with a a single 1-1/2" vent. You can't wet vent any other fixtures such as kitchen sinks, laundry trays or washers.
  6. Numerick

    Numerick New Member

    Messages:
    9
    Location:
    New Hampshire
    Tom: Just curious, under UPC what is the allowed distance for the toliet?
  7. Numerick

    Numerick New Member

    Messages:
    9
    Location:
    New Hampshire
    Thanks, asktom. I cannot vent the kitchen through the roof for structural reasons. Would the loop vent or AAV valve be OK to use. There really is not any way I can vent the sink. Thinking maybe a 3" combination waste/vent pipe (instead of AAV or Island Loop) would possibly work for the sink provided it was place at the top of the waste stack?
  8. asktom

    asktom Member

    Messages:
    519
    Location:
    Victor, MT
    The maximum distance for the toilet is a developed length of 6'. It is measured from the top of the flange, along the center of the pipe to the edge of the vent.

    A loop vent would work. I don't know if AAVs meet code in your area in your area, if they are, it would need to tee in above the toilet. Using 3" for the kitchen would make it vent like a champ, but it wouldn't drain as well as 2" because the water would be spread out more in the pipe and not wash junk down as well. Don't use 3" for the kitchen.
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