What started as a slow toilet, now non flushing except 1-2 times in morning, has turned into a toilet bowl that won't hold water but the tank still does. The tub is first on the line, then the toilet, then 30' to septic tank. Snaked through the vent, got a lot of greasy goo, but still toilet wouldn't flush. We filled the tub then let water out, it started to fill the toilet bowl, then emptied down some and continued emptying until just the very bottom of bowl had water. No cracks in the tank cylinder. Thought we'd try degreaser for toilet clog, but now not sure what we're dealing with. Clogged vent?

I have one that most repair plumbers miss.. Look down at the bottom of the bowl. If there is a small hole, then that is a jet that starts the syphon action. If it's clogged the water will just swirl around and slowly go down leaving solids behind. Take your finger,(UGH! ) and run it around the inside of the opening. Over the years minerals build up and cut down on the syphon (flush) action. If it is rough or you feel build up, take a table knife and put a bend in it to get around the curve in the bowl and chip and scrap it clear. Next take a coathanger and clear out the holes around the rim. They start the swirling action. And last, check the water level in the tank. It should be 1/2" below the top of the over flow tube. And speaking of the overflow tube, Make sure the small 1/8" tube from the ballcock to the white overflow tube is connected so it discharges in it and that it's flowing when the ballcock fills. This is what raises the water level in the bowl. For a good solid flush they all have to work together. Hope this helps and thank you for rating my reply.. Tom