Vanity Sink Waste Stub Out Too Low

[Schwarz633]

I'm replacing a pedestal sink with a vanity that has an open shelf underneath, so the bottom is rather high. Based on what I've read and my limited understanding of venting, I'd like to know if what I've mocked up in this picture is acceptable. Any and all suggestions and comments are welcome.

 

[Reach4]

Acceptable, except that the AAV has a minimum height above the santee. I am thinking 4 inches to the bottom, but you check. I think you could improve it a bit more by rotating the santee a bit more CCW as viewed from the top. You have to keep the trap arm at least 3 inches long (much of which is inside the trap adapter) if that is a 1.5 inch trap. On the other hand, maybe moving the trap around would take up space you want to keep clear.

Another way is to notch out the sink shelf to clear the trap, so no AAV needed.

 

[Sponsor]

 

[Jadnashua]

You generally want the aav higher up, but not so high that you can't unscrew it for eventual replacement. They can last a long time, but not forever. As low as it is, if there's even a bit of restriction in the drain line, crud could back up into it, spoiling its ability to seal, and worst case leaking out.

 

[Schwarz633]

I can definitely raise the AAV, it's just sitting on top of the santee in the picture. The Oatey diagram shows 4" minimum from the top of the santee horizontal pipe to what appears to be the bottom of the AAV threads. The diagram is somewhat vague, but I think I can include part of the AAV adapter in that measurement.

My P-trap is 1.25" and there's 3" of straight arm exposed outside of the adapter.

Cutting out the bottom of the vanity is what I'm trying to avoid.

 

[Jadnashua]

Water exerts about 0.43#/foot of elevation and a clogged drain could allow waste to back up, which is the reason they want the thing raised some. At 4", that's only a third of a foot, and would be less than 0.15# of pressure there, but that's enough.
The seal on the AAV is just a rubber flap. Getting crud underneath it will prevent it from sealing, potentially letting sewer gasses out all of the time, or in a real clog, leaking waste.

 

[Reach4]

One more thing: it may be that bottom elbow should be a long sweep, since you are transitioning vertical to horizontal. I don't know what Wisconsin calls for for that.

Maybe use a combo and make the straight port a cleanout.

 

[Schwarz633]

One more thing: it may be that bottom elbow should be a long sweep, since you are transitioning vertical to horizontal. I don't know what Wisconsin calls for for that.

Maybe use a combo and make the straight port a cleanout.

Is a combo a santee?

 

[Reach4]

See https://www.co.lincoln.or.us/sites/..._-_helpful_hints_residential_construction.pdf

page 2, 2nd one down on the left "combination Y-1/8 ". Don't worry about black vs white plastic. That is mostly a regional thing.

The combo/combination is named that way because it is like a wye combined with a 45(1/8 bend).

The downside is that it brings the aav stack farther from the wall.

 

[Schwarz633]

I tried a combo tee and just couldn't make it work. I swapped the elbow for a santee with a cleanout and raised the AAV.

 

[Schwarz633]

If I hadn't gotten ahead of myself and shortened the 1-1/4" tailpiece I guess I could lower everything by a couple of inches. My first thought was to maximize storage space by having the trap as high as possible. It doesn't look like Menards carries a 1-1/4" x 6" flanged tailpiece, $8.00 .