Combination wye or sanitary tee to tie into vertical drain?
Asked Jul 7, 2008, 11:23 AM
I am connecting a washer standpipe trap arm to a drain.
From the trap, the pipe will run a few feet to a vertical drain/vent. That drain/vent also serves as the drain for the laundry sink (which connects just above where the standpipe trap arm will meet the drain vent) and, above that, a vent for the sink in the adjacent bathroom. I will run a separate vent off the standpipe trap arm, before it meets the vertical drain/vent. This standpipe vent will reconnect with the drain/vent above the other vent connections and above the flood level of the washer.
Question: I understand that a sanitary tee (insted of a combination wye and 1/8th) should be used where a trap arm meets a vertical drain/vent, so that the vent does not get choked off by the water flow from the fixture/washer. But is this true even if the washer standpipe is separately vented before meeting the drain/vent?
If not, it seems like using a combination wye would be preferable to the sanitary tee, since it will better direct the strong discharge from the washer.
Thanks for any thoughts!