ok, I'll try to make it as much like cliff notes as possible since I tend to be wordy
1) have been cooking a lot of meatballs recently in a pressure cooker, and foolishly letting the grease residue be "washed" off in the dishwasher, assuming it would stay emulsified all the way to street. Nope.
2) was rushing with the dishes early this week and let more rice grains then usual get in there...uh oh...
3) had a backup, but it was never a non-moving one...just a major slow down. Oddly, plunging, even with the other sink drain unstoppered, always helped it move faster. I think this is part of the mystery...more in a moment

(btw kitchen does not have a disposal, home inspector told me that older houses w/iron pipes often don't)

4) tried various things...first a bit of lye because I've used that successfully before when it slowed down. Not this time. Bought one of the el-cheapo $20 snakes and got it 6' in before I couldn't go any further. That was a struggle. Pipe was crazy gunked up with black goo.

5) Used 1/2 a bottle (4X the normal dose) of Drano Buildup remover, overnight. This seemed to help, but it was still slow. Plunging made it move faster this time.

6) Notice the AAV for the first time. Wonder what the heck it is and read up on them. Determine it's an old non-code compliant spring loaded one...decide to shell out for a Studor mini-vent top of the line one the during the next HW store outing. Also buy some liquid-plumr "urgent" formula, to try caustics one more time.

7) let liquid-plumr work for 90 minutes. Put on new AAV valve.

8) STILL slow. I finally get curious about the AAV valve, not even trusting the new one, and completely remove it. Presto...suddenly the water drains like a champ! I easily get 5 gallons from various buckets down in one huge gulp. Mind you I had never tested without during the initial backup issue, because I wasn't even aware it was there the first day.
OTOH, it surely appears the buildup remover and caustics probably helped.

FFeeewww. SO, question is, WHY would the drains appear to work fine w/o the AAV, even a top of the line one, and run slow with it? The odd thing is just running the tap at medium won't clog it. You have to be emptying the dishwasher or pouring a gallon of water down as though draining pasta. Then, it will slow down about 1/2 way through the gallon...but a plunge or two will get it running again. This is w/the AAV valve. W/o the water now runs through the drain faster than it ever did before, probably because of all the buildup removal and snaking I did.

UPDATE:
found this thread, which seems to describe my issue
http://www.plbg.com/forum/read.php?1,333335

like the poster there, though, what I can't figure out is why there is no sign of a back up at all, when air is allowed to escape. (i.le., the AAV removed) FWIW I'm letting a few more ounces of the build up remove soak down there tonight, in case this is all still being caused by a bit of minor blockage. Maybe it will help more now that things are mostly moving again. ( after putting about 10 gallons plain water through to make sure the caustics are gone) BTW on the other side of the house where most of the plumbing is (bathrooms) there is a typical roof vent stack. I know those getting clogged can cause problems, but the timing is too close to my rice in dishwasher idiocy for me to think anything else was the cause. And all the drains in the bathrooms are working great)

This post was edited by davidrt28 on Fri, Jan 10, 14 at 1:08