I have two toliets in my Duplex, which is on a 30 year old septic system. One toilet flushes down great. The other when flushed doesn't begin swirling right away if at all, the water bubbles in from below in the trap, then it will swirl a little, and act as though it is clogged then finally it will flush..sorta. I have snaked this toilet on several occasions, but nothing helps. I have checked and there are only two vents on the roof for the whole place. One for the kitchen, full bath and the other for the 1/2 bath and washing machine. I have been up there and run a garden hose down both with no problems noted. So I am contemplating next pulling the toilet up and checking it out. And/or replacing the stool all together! Thanks for any help or insight.
Take Care,
Griz

 

From your description it sounds like the jetways are clogged. When the water leaves the tank and enters the bowl, it goes into passageways in the wall of the bowl. Some of that water should come out all around the rim, to wash it down, and the rest should come out a hole near the bottom of the bowl. That hole starts the siphon action.
If the water does not come out very fast, as in it takes a while for the tank to empty, then the waterways are clogged.
If you take 2 or 3 gallons of water and dump it quickly into the bowl, it should flush right down. If it doesn't, then the drain portion is clogged.
If this problem just appeared, look for a clog. I have encountered toilets that I could snake, but would not flush that had objects stuck in the top of the trap, such as a broken wine glass or a clear plastic scoop.
Let us know what you find.

 

It indeed does flush better since I cleaned out the jetways, but it still seems to be slow and backflow like from the bottom before it begins swirling. I don't recall seeing a hole at the bottom other than the drain....maybe the original toilet from 1976, when the duplex was built....I am happy with the results overall..if it becomes a problem, it will be taken up and checked out more thoroughly. Thanks for your insight!!
Take Care,
Griz