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Posted by Wayne Whitney on April 18, 2008, 1:19 pm
OK, I think I've answered all my own questions except one. So:
> I'm planning the DWV plumbing for a kitchen island sink and have a
> few questions about the requisite vent loop. We're on the 2006 UPC
> here and air admittance valves are not allowed. I'm using the
> following image as a reference:
>
<http://www.rd.com/images/tfhimport/2003/20031001_Ask_Handyman_page001img001_size2.jpg>
>
> (1) The drain line will be 2". Is it necessary or useful to enlarge
> the vent from the usual 1.5" to 2"?
Not necessary, and not useful given concern (4) below.
> (2) I assume that there is no horizontal separation requirement for
> the two vertical legs of the loop. So from the fixture san-T I can
> come up to a street 45, a 90, and then a street 45. Is that
> correct? Also, is that a vent 90 or a long-turn 90?
UPC 909 says I can use a one piece return fitting; otherwise I have to
use the 45-90-45 pattern. The 90 is a drainage 90, but need not be
long-turn. Nothing wrong with using street fittings.
> (3) Is it important that the vent leg of the loop connect to the
> drain downstream of the drainage leg of the loop, rather than
> upstream?
Yes, the vent always attaches downstream of the trap.
> (4) To get both the horizontal vent and the horizontal drain to fit
> in the joist cavity, I'd like to minimize the height difference
> between them. In usual pattern, the vertical vent leg comes down
> into a san-T for the horizontal vent take-off followed by a combo to
> tie into the horizontal drain.
Actually, for the UPC, the vertical vent leg has to come down to a
combo for the horizontal vent take-off.
> I'd like to roll this san-T/combo over to 45 degrees from the
> vertical, by inserting a 45 elbow before the san-T. Is there any
> problem with this?
Still not sure of this, whether I can roll the combo-combo over 45
degrees. Any comments? Or any other ideas on minimizing the height
difference between the horizontal vent (foot vent) and the horizontal
drain?
> FWIW, there will be a regularly vented sink upstream of the island
> sink, and I plan to run the island vent over to the this area to
> connect with the regular sink vent. Thanks in advance.
No other fixtures can be attached upstream of the loop vent, so I have
to split my drain line downstream of the loop vent to accomodate the
other sink.
Cheers, Wayne
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