I am renting an upstairs apartment where the homeowner installed a kitchen sink. The water takes over an hour to drain, I looked underneath and found this: Kitchen Sink, venting issue. - Imgur (http://imgur.com/a/UaXcb)

After the P-curve, the venting line is the wimpy clear plastic hose coming off the T-Joint. It goes up to a hole in the counter top above sink level, ending in a dishwasher air gap. There is no dishwasher, so only one of the two ports on the air gap have anything connecting to it.

From reading the sage advice of Speedball1, I'd think it could be fixed by replacing the T-joint and installing an AAV, like this: http://www.plumbingsupply.com/images/studor-aav-diagram.jpg But in my state AAV's are illegal, and last year Studor attempted to sue Minnesota, but lost. Now I'm lost. We're hoping to save the homeowner (a little old lady) some money, but you can only fix a problem with "chewing gum" for so long.

Sincerely, Joel

Hi Joel

I'm afraid you are way off with your interpretation of the plumbing under that sink... ;)

In fact, what you have there is a legally vented sink! The sink appears to be vented as an ISLAND SINK (see image of similar vent below)... as long as it connects into a vent in the walls somewhere... looking pretty exact in terms of engineering specs. That I can see!

The clear tube isn't a vent as much as it is the right side of a FUTURE D/W connection via the air gap... since no D/W, no need to connect the other side, right?

Anyway, what you have here is a clogged drain or a clogged island vent, or even both if the drainage problem is as bad as you suggest, as it is possible that the drain has been backed up a while and using the vent as a drain!

If you are lucky there is a cleanout under the sink (should be) and you guys can try to rent a drain machine and snake the drain. Otherwise, the landlady has to bite the bullet and pay to have this cleaned out... simple as that!

Glad to discuss more if you want...

Mark

Mark,
Thanks for pulling me out of that rabbit hole. ;-)

Liquid Plumbr + Plunger + the confidence you gave me that this was a simple clog and not something more complicated = A working sink!
Joel
http://i.imgur.com/C0Twe.jpg

Thank you for taking the time to post back AND to draw up my avatar... fun way to say thanks!