I have an older house with a lot of “grand-fathered” plumbing problems. The drain pipe in the wall looks to be about 2″ with a 90 degree elbow leading to the sink trap. The elbow has a reduction ring to allow for a standard sized pipe to be screwed in place. The pipe exiting the elbow to the sink is approx. 3″ long. So far I’ve tried the following to either unclog and/or remove the smaller piping and the reduction ring.
1. Heating the connection with a torch.
2. WD-40
3. 3 in 1 Oil
So far I’m still unable to turn the smaller pipe or even loosen it.
4. Drain auger will not make the turn in to the elbow.
5. Standard stored bought drain openers, i.e. Drain-o, Liguid Plumber and such have now effect. Drain may run run clear for a day or two but clogs shut again.

My experience with a kitchen sink drain is that because the sink gets waste that has fats, the branch line gets coated with fat deposits. In my case the only solution was to route the branch line. If you can’t get a routing machine in the branch line then you may have to open the wall and correct the plumbing so you can get one in.

I hate to say the obvious but be sure but be sure you’re turning the fitting in the right direction. Under a sink can get confusing. Right tighty, lefty-lucy. It might help to use a pipe wrench and tap it with a heavy hammer or mallet to help break the seal if it will fit in there. There should be an access point in the branch line if the house had the plumbing put in correctly. But unfortunately in older houses this isn’t always the case. When a fitting won’t turn it’s probably because it’s bound by corrosion. You probably need a bigger pipe wrench or better leverage. Under a sink is a miserable place to get good leverage. If there is access from behind by opening a wall, then possibly cutting the pipe with a sawsall and replumbing the sink so it isn’t a problem in the future might be a solution. If you do have to re-plumb it, be sure it has a vent and an access point for routing the branch line. You may end up having to repair someone else’s mistake. Be careful when mixing WD40 with a flame. It’s mostly LPG and is extremely flammable, explosively flammable. The joy of home ownership.

OK, I think what’s needed here is a visual. You’re looking at the section that’s giving me fits.
1. pipe from the trap
2. that white ring is the reduction ring so the small pipe will fit in to the
rather large elbow.
3. the elbow
4. the 2″ drain pipe
Incidentally i did try the shop-vac.. no luck auger wont make the bend in the elbow. Can’t turn the smaller pipe (probably rust or gunk) can’t turn the elbow because the smaller pipe would punch a hole in the opposit wall (dinning room)

What kind of floor do you have, is it a cement slab or is there a basement or crawl space below? Or possibly on a second floor? There should be an access point in the branch line, somewhere accessible, that your snake would clean the branch line through. Sometimes you have to run the snake through the vent from the roof but you have to figure out the layout of the vent and branch line to tell if it’s possible. If it’s possible to go under the floor, follow the branch line to see all the branches in it. One of them should be an access point. It might be buried by an outside wall. It also could be inside the house somewhere too. Only you know the layout of the house. Solving a sewer problem requires a little detective work. My guess it’s a fat buildup on the branch line. Hair usually comes from a shower or bathtub drain and food byproducts come from the kitchen sink of which fat is the one that leaves the most lasting effect. It builds up in layers and closes off the line by restricting it. Stuff gets caught in it too. Are there any other drains having a problem too? If there are, that would tell you something more about the clog. You have to look at the whole layout of the sewer system. If there are two branch lines having a problem it would indicate a problem further down the line, like maybe roots or a foreign object that was flushed. You have to use some deductive reasoning to figure it out.

I have one of those old type drains where the plug is a metal thing attached with a hard stem to the sink and tub. I can’t take the plug out, so I have to pick with a toothpick or slim thing the soot that’s clogging the top only. Sometimes I can put a long thin thing in it and it might get rid of some of the soot, but I wonder what can I do about this? Vinegar and baking soda? I can’t get a good water flush over that because with the drain plug there, it doesn’t allow a full flow of water to go down the drain. I even wonder how I can simply break that dumb drain off of the tub and sink. It doesn’t do the job for plugging it up anyway.