I am adding a first floor half bath to 3 units in my triplex. I want to be sure I am UPC compliant with this plan.

1A is my preferred option, but 1B is an alternative, depending upon the easiest route to get the vent to the attic.



The main question is about the fittings to use (red circles). I want to be sure I need to use Ys and 45s (or combos) rather than sanitary Ts in each case, and in case 1B, if the LAV to drain connection should be horizontal or turned up 45 degrees.

The 3” main drain is a new drain that will only service the 3 half baths, as the existing drain is only 3”. I will tie the two 3” drains into a 4” Y before going into the 4” sewer line. The WC is less than 4 ft from the LAV and less than 6 ft from the main drain.

  • Is there a difference between 1A and 1B? Or am I just not seeing it?
    – mmathis
    Oct 21 '16 at 20:50
  • 1
    @mmathis the difference is that in 1B there is a horizontal offset before going vertical to the LAV.
    – pdd
    Oct 21 '16 at 20:55
  • @pdd Oh, yup, there it is! My bad!
    – mmathis
    Oct 21 '16 at 20:57

Both drawings look correct. The areas circiled in both options whoud use the same fittings: wye with 45 elbow (or a combo fitting). Tees are only used when drainig from horizontal to vertical (such as the fitting picking up the LAV's trap arm) or in venting (your LAV vent connecting to the branch vent).

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