Ok, I have read many questions and answers to this question, but none of them are what mine is doing. Buckets of water poured down don't go down, holes aren't clogged, all the guts in toilet work fine. I have logged it--sometimes I get 1 or 2 flushes that actually work, there has been a time I actually got 30 flushes. Sinks, tub, shower, other toilet all drain & work correctly with no bubbling, stink, etc. This toilet will fill to almost overflowing, then takes an hour to drain (no solids, minimal toilet paper). We have snaked with 3' and nothing. Only me here, no children or anything dropped in. A toilet is a simple fixture--people question its a defective toilet?! Venting? Pipe was cut in attic thinking vent issue and still nothing. Here's the plumbing: in crawl there is a 90 degree into a 45 degree, a 4' run with a 1/16" per foot slope (supposed to be 1/4" slope per foot), vent is 12' away from toilet before going upwards then reduced to 1 1/2" pvc, then 7-8' up in ceiling with six 90 degree elbows, about 12-15' run in attic and goes back to 2" pvc to meet an existing toilet, both vented out same pipe. Toilet is American Standard. Help?!
Your DIY answer is: Call the plumber that installed it.
If that does not work, call your state licencing board, and determine who the bonding agent is for the plumber (it's a licenced plumber, right?)