Tiny House Plumbing

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by BlakeR, Apr 21, 2019.

  1. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado
    Hi,

    I am building myself a tiny house on a trailer. I have been using old forum threads to answer questions and to learn how to install my plumbing system. I have reached a point where I have specific questions regarding my build and I am hoping to get some answers.

    Thanks,
    Blake

    General Information
    I am building in Colorado at an Elevation of 6500 Feet.
    I am building on a 26' trailer with a 6" wood sub-floor.
    My drain lines will exit below the trailer deck, so I want my p traps in sub-floor or under cabinets to prevent freezing.
    I am planning on using 1 1/2" and 3" drain and vent lines.

    Questions
    Can I vent my bathroom sink, tub and toilet with a Studor Minivent under my bathroom vanity cabinet?
    I plan on installing three Studor Minivents for my entire system. (kitchen sink and washing machine drain)
    Can I drain my tub with in my 2x6 sub-floor with the following setup? Tub drain -- p trap -- 6" straight pipe -- 90 degree long turn -- exit below trailer deck into main drain

    I have attached a sketch of my floor plan with idea idea of my drain plan.
     

    Attached Files:

  2. WorthFlorida

    WorthFlorida Broad-Wing Hawk

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    Occupation:
    Retired
    Location:
    Orlando, Florida
    https://up.codes/viewer/colorado/ipc-2015

    You start here with IPC codes. You’ll need to find out where you plan to use this tiny house if it is classed as a camper on wheels or a trailer type home that may require anchoring to a foundation. That will impact code requirements if any that are applied to tiny houses.
     
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  4. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado

    Where I live it is considered a recreational vehicle. I will not have any building inspections. I will have traditional RV style hook ups for electrical, water and a sewer line. I work as a residential construction manger and I am familiar with many building codes, but I am not an expert in plumbing. As much as I respect the code, my main concern is proper functioning of the Tiny House, not code compliance.
    Thanks,
    Blake
     
  5. Terry

    Terry Administrator Staff Member

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    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    It would be better if it was the toilet as the last fixture.
    Wet venting is for bathroom groups, so the lav could vent a tub and the toilet.
    The kitchen sink needs it's vent, and so does the washer.
    At least one atmospheric vent through the roof is needed when using AAV venting.
     
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  6. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado
    Hi Terry,

    Thanks for the response. If I need to install an atmospheric vent, I would prefer to do so on the exterior of the house, instead of through my walls. Is there an issue with venting on the outside of the house since my drains lines will be outside of my house as well? If running an exterior vent on the outside of the house, could I get away with running the vent to a certain height (4' above drains lines), instead of to the roof height? Does the vent just need to be above the fixture height (sink overflow)? If the toilet should be the last fixture, should I run the vent on the exterior of the house just past the toilet?
     

    Attached Files:

  7. MASTERPLUMB777

    MASTERPLUMB777 In the Trades

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    Occupation:
    Retired Master Plumber
    Location:
    Texas
    Min vent size is 2" ! p-traps have to be located tight under the fixtures "NOT" below the flooring ! Exception Tub or Shower
     
  8. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    Washing machines take a 2" trap and standpipe.
    Toilets use a 2" vent.
    The purpose of venting above the roof is to disperse the sewer gas into the prevailing wind. Install it below your nose, and guess who gets to smell it?

    Your drawing doesn't show much except that you plan to run pipes to those locations.

    [​IMG]

    Here is a nice link to Bert Polk's plumbing tips
     
  9. WorthFlorida

    WorthFlorida Broad-Wing Hawk

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    Though this is classed as an RV, be careful not to create S Traps since they have more of a tendency to be siphoned dry.
     
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  10. BlakeR

    BlakeR New Member

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    Apr 21, 2019
    Location:
    Colorado
    Got it. I will make all of my vents 2"! Thanks
     
  11. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado

    Thank you for the riser diagram. I will vent with 2" pipe and run my atmospheric vent to the roof.
    Thanks
     
  12. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado
    Yes! I've read that the run of the pipe past the p trap (trap arm?) needs to be twice the diameter of the drain before turning down again. My shortest trap arm run will be my tub p trap arm, where I need to bring it down in the shortest run possible.
     
  13. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado
    In the first image of the tub drain, I am going to try to run my p trap and trap arm in a 6" subfloor, before exiting below the trailer deck. I think this may be possible as my 1 1/2" p trap is about 5 1/2" tall.

    In the second image, it shows the trap arm being twice the length of the drain diameter. Is this correct?
     

    Attached Files:

  14. Reach4

    Reach4 Well-Known Member

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    Sep 25, 2013
    Location:
    IL
    That picture still shows an S-trap. The standpipe needs a vent before the drainage goes down after the trap. That vent could be an AAV.
     
  15. BlakeR

    BlakeR New Member

    Joined:
    Apr 21, 2019
    Location:
    Colorado
    Is this now a p trap now that it is vented?
     

    Attached Files:

  16. Reach4

    Reach4 Well-Known Member

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    Sep 25, 2013
    Location:
    IL
    Yes. 2 inch pipe for a washer standpipe.
     
  17. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    If you run 2 inch pipe from the roof for the lavatory, that will probably also vent the downstream toilet.
     
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