It was taking around 24 hours to drain just ~1—3 liters of water in my kitchen sink. After a huge effort and expense, I finally fixed it without demolishing the kitchen – which would have been my next and final move. Sequence of events:

  • tried many boiling pots of water to melt any grease

  • tried 3 varieties of cheap drain cleaners, the contents of which are not always known due to trade-secret protectionism (when most likely it’s just bleach or lye). Also poured down ordinary household bleach (likely in the typical 15% concentration).

  • removed trap and all joints… down to just the wall opening.

  • snaked the line with a simple snake. Took all day to get the snake inserted because apparently there are many hard 90° turns. It kept hitting a wall & required lots of force and spinning. Poured boiling water in with the snake inserted and it drained quickly. Pulled the snake out and it was slow again. Repeated the process several times and one late night just left the snake inserted figuring i would deal with it in the morning. Pulled the snake out and it was permanently curled up like a pig’s tail. I guess it hit such a hard turn that it coiled up inside rather than progressing down the line.

  • cut off the meter or so of curled up snake. Used a blow torch to soften the new end and pulled on it with pliers so the end was a little stretched as they come from the factory. Bent some copper pipe, drilled a hole in it, threaded it, added a screw, so I could use the pipe to force the snake to spin close to the drain entry point. Made no difference, and after the last use a new kink occurred higher up so the snake is ruined.

  • every week poured a different brand of enzyme based drain cleaner following warm water to warm up the pipes & let it sit for 6+ hours. Used 3 different enzyme brands on weekly rotation.

  • tried a two component drain cleaner: ① sodium hydroxide + ② sodium hyphchorite with sodium hydroxide (yeah, sounds redudant but bleach is really in both components)

  • built a leaf blower connection using a series of PVC pipes, some softened with a heat gun to tightly fit to the blower. Gave it full force and got no results.

  • bought an “auger”, which is a snake inside a box with a crank & essentially the same features I added to the simple snake. It also hit a wall & could not make one of the turns. It came out clean, but with a kink from pushing on it (which is what you do when nothing else works).

  • asked IRC chem channel for advice. It is chem related but they really do not want to hear too much home improvement chatter. Can’t say I blame them but the best chem knowledge would come from chemists not home DiYers. Someone said get sulfuric acid “if you can”.

  • (illegal) found a source for sulfuric acid, which is illegal for consumers in my region. Poured only ~30ml down the drain (much less than directed but this stuff is costly), heard it sizzling. Instructions say wait 15 min then pour cold water. I waited 20 min before topping off with cold water. No progress. Took all night to drain as far as i could see. Poured ~300ml more down the drain. Sizzling. Smells like vomit. Bits of white junk show up… probably part of a giant “fatberg”. But still no progress. When the visible drain is clear, added ~170ml more (total of ½ liter at this point). Still no progress.

  • bough a bicycle pump style plunger. This thing can mate directly with the pipework. Used it just to push water down. It worked to just push the water further down, but when topping up with water it’s still clogged. So then I did the pumping action with the plunger. I wanted to resist this because I don’t exactly want sulfuric acid getting sucked into the new plunger. Finally the clog is clear. Cleaned the plunger with several full pumps of clean water.

Now it drains 5 liters of water in 29 seconds. Wow what difference. I can even see the tornado in the sink, which I don’t recall if I ever saw that in this sink.

Costs of chemicals and tools were, shit, roughly like:

25 snake (destroyed) 25 auger (cheap compared to most augers, kinked) 20 brand A enzymes 18 brand B enzymes 21 brand C enzymes 5 drain cleaner brand X 8 drain cleaner brand Y 10 drain cleaner brand Z 20 1 liter sulfuric acid 15 PVC parts for leaf blower 8 simple plunger (useless because it just pushes trap water out the overflow) 10 bicycle pump style plunger (apparently the most critical tool)

IMO the sulfuric acid was essential for loosening whatever I had in there (probably a fatberg), but the final success came from the bicycle pump style plunger directly on the line.