(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 4 of 4

Thread: VTR sizing

  1. #1
    DIY Senior Member DavidTu's Avatar
    Join Date
    Dec 2009
    Location
    Seattle, WA
    Posts
    229

    Default VTR sizing

    In a moment of hubris , I had two 2" VTR roof jacks installed for a 3" drain. <doh!

    [Mea culpa: I am aware of the area requirements for VTR but I didn't have my book or calculator with me and I knew that two 3" pipes > 1 4" pipe, and same is true for all other pipe sizes relative to the next size up so I errantly ASSUMED that the same held true for two 2" > one 3" in area.... EXCEPT, it turns out it's not: 2x2" = 6.28si vs 3" = 7.06si).]

    My venting is mainly all 2" runs. I'm in Seattle and the Chief Inspector has previously told me that they do NOT require a continous run from the sewer through the roof at full-size of the sewer (ie. 3" from sewer through roof). Rather, as long as each fixture is appropriately vented and as long as the accumulated dfu's are within spec all is good (provided we meet the area requirement which we did not do).

    My question is: a) will the inspector definitely require me to upsize one VTR to 3" (leaving other 2")? ... i.e. should I see if it sneaks by or just go ahead and do it now! and (b) is there any real-world benefit to doing this inasmuch as venting to satisfy the dfu's is easily handled by 2" vent pipe (24 dfu capacity, 13 used) and really all that will happen is in the attic I'll upsize the 2" pipe to 3" when I join a couple of 2" pipes there. NOTE: I do plan to use a AAV for kitchen sink.

    FYI: one 2" VTR is serving a toilet + lavatory (4 dfu), the other is serving laundry tray & clothes washer standpipe, toilet, lavatory, tub/shower, and a kitchen sink w/ disposal + dishwasher vented on AAV (13 dfu including KS)

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,405

    Default

    Some places require the vent to be larger because of potential frost buildup. That probably isn't an issue in Seattle.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Senior Member DavidTu's Avatar
    Join Date
    Dec 2009
    Location
    Seattle, WA
    Posts
    229

    Default

    So is the consensus that I'd be OK leaving both at 2"?

    Btw, if I could locate some 2.5" pipe it would work for the area requirement AND fit inside the '2-inch' roof jack since it is a lead jack it seems larger than 2" abs pipe and looks like it could accomodate the 2.5".

    (Also, is there some minimum length I'd have to have 3" pipe inside, were I to upsize the jack?)

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,653

    Default

    It would have to be 3" from the point of juncture of two other vents. I assume this is a tile roof, so adding a 1 1/2" vent may not be a possibility, but that would satisfy the inspector. IF he only sees TWO 2" vents he will know the area rule was not met. In the future, when you want compare areas, just square the radius, (forget about pi, since it is a constant), and do the computations.

Similar Threads

  1. DWV Sizing
    By Twinpeaksr in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 4
    Last Post: 01-14-2010, 08:19 AM
  2. Vent sizing?
    By LO in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 17
    Last Post: 04-20-2008, 03:10 PM
  3. Pump sizing?
    By Vetteski in forum Pumps and Tanks Well Forum & Blog
    Replies: 7
    Last Post: 03-12-2008, 05:37 AM
  4. pex sizing
    By mikeyvon in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 4
    Last Post: 01-22-2008, 02:10 PM
  5. DWV Sizing
    By Spaceman Spiff in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 2
    Last Post: 07-27-2005, 02:06 PM

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
  •