(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 9 of 9

Thread: fixture units

  1. #1
    In the Trades ilya's Avatar
    Join Date
    Dec 2009
    Location
    Akron Ohio
    Posts
    105

    Default fixture units

    Twinpeaksr's post and Terry's reply brought something to a head for me. I don't understand how to use fixture units for supply or DWV. I only know they help calculate pipe sizing requirements based on fixtures served. Can someone here help please? Thanks
    not a licensed plumber

  2. #2
    Plumbing Designer FloridaOrange's Avatar
    Join Date
    Dec 2005
    Location
    SW Florida
    Posts
    1,317

    Default

    You get drainage fixture units and that relates to the pipe size (somewhat) and more to the venting pie sizes.
    Water supply fixture units relates to water pipe sizes.

    What are you trying to understand?
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  3. #3
    In the Trades ilya's Avatar
    Join Date
    Dec 2009
    Location
    Akron Ohio
    Posts
    105

    Default

    I'm starting with the assumption that there are charts for these units, and that x number of units requires a certain size pipe, be it supply or DWV. A lav sink would seem to have less Fixture Units than a shower, for example. But that's the extent of what I think I know.
    not a licensed plumber

  4. #4
    JMan plumber/gasfitter iconicplumber's Avatar
    Join Date
    Jan 2010
    Location
    Fort Saskatchewan, Alberta, Canada
    Posts
    7

    Default

    i wish i could help but if it was easy everyone would be doing it.

    the dialogue would fill this page and more on how to properly size dwv(drain waste and vent), that being said if you had a more specific question i might be able to help you out.

  5. #5
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    Location
    San Diego
    Posts
    9,001

    Default

    Each plumbing code has charts of drain and supply FU numbers. The Wisconsin code happens to be available on line. Go to page 8 of this pdf ( it is page 26 of the document) http://www.legis.state.wi.us/rsb/code/comm/comm082.pdf
    Last edited by jimbo; 01-14-2010 at 06:28 AM.

  6. #6
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,633

    Default Dfu

    Drainage sizes are dependent on the number of fixtures connected to the pipe and the pipe lengths. Water fixture units are also based on the number of faucets, BUT, there is also a factor applied because they know that not every faucet and toilet is going to be used at the same time. Therefore, water supply tables vary according to the building's usage and number of occupants.

  7. #7
    Retired prof. engr. gator37's Avatar
    Join Date
    Nov 2009
    Location
    Alabama
    Posts
    108

    Smile Good answer Jimbo

    Good answer Jimbo.
    A fixture unit is a fictitious number (from a code which is based on years of collective experience) assigned to a fixture (just a number assigned to a fixture), be it waste, vent, water supply, etc.
    It provides a diversity to sizing, in other words if you had two 2" lines from a fixture, you would not size the collector pipe for twice the area of one 2" pipe. This is done because it not highly likely that all the fixtures would be turned on at the same time.
    Some codes like the NPC or the IPC have examples on sizing in their appendix.

  8. #8
    Retired prof. engr. gator37's Avatar
    Join Date
    Nov 2009
    Location
    Alabama
    Posts
    108

    Default another Good answer HJ

    another Good answer HJ

  9. #9
    Engineer Twinpeaksr's Avatar
    Join Date
    Jan 2010
    Location
    Denver, IA
    Posts
    26

    Default

    On the DWV side, is there a down side to oversizing the vent or drain? I can't think of any but thought I would put it out there.

    Thanks!
    "Now Grab a Brick or go to Hell." - H. Simpson

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •