Re: question on running a vent
Posted by Deb on March 25, 2004 at 14:41:22:
In response to Re: question on running a vent
: I am relocating my sink to the opposite wall. On this new wall is a tub drain from the above bathroom.

: We plan to tap into this exisitng inch and a half galvanized drain-well we want to replace w/ pvc and join the new sink dain into the tub drain.

: My question is I do not see a vent for this tub drain- my guess is that it is vented underneath somewhere?? If it is indeed vented somewhere can I just tie in the new sink drain and not have to run a separate vent b/c there is one for the tub already and the new sink drain will be part of the existing tub drain?

: your help and opinion is greatly appreciated,

: regards,
: Harvey

Generally speaking, you cannot connect a drain in the section of pipe that runs from a fixture p-trap to its vent (this section of pipe is called a trap arm). On a sink there is no way to connect without venting the sink. Any attempt to connect to the tub drain will create an s trap. S-traps will siphon dry and allow sewer gas to enter the house. The sink will need a vent that rises straight up at the sanitary tee that is the drain/vent/trap arm junction. It can 90 or join with other vents 6" above the flood rim level of the fixture. If this is not a bathroom sink (a lav), but a kitchen sink, you need to use 2" drainage pipe.
The Pipewench

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