I have plunged
I have used 1.5 gallons of drian cleaner
I have used short rooter
I have removed toilet and used 50 ft rooter - no risistance!!
Tipped gallon of water down hole no probs
Could it be that there is a problem with the actual toilet bowl>
(All other toilets on same upper floor flush just fine)

Any ideas??

Is the water level in the tank up to witin an inch of the top of the over flow tube? Also check the small hoes under the mouth of the toilet, you can't see them but feel them and probe with a straightened coat hanger. Also stick you finger into the 1" hole at the base of the toilet sump area, this is what starts the siphon action. How long has it been slow?

Thanks to ballengerb1 - problem resolved. Blocked hole at base of toilet sump was the issue - cleaned out - Now works fine. Great answer to my problem and well done to Ask me!

I have exactly the same problem and have tried all the same things. I even removed the toilet and brought it out on the lawn and stuck a garden hose in every orifice. My toilet doesn't have another hole at the base of the sump that I can see or feel. That is what seems to be the problem though. I can't tell where the overflow tube goes. There is no suction or siphon or even much swirling. Interesting though; if I plug the overflow tube and flush it seems to start swirling and go down but slowly. So seems again to be a siphoning issue. The toilet is 12 years old and hasn't flushed very good for the last 8 years since we've been here. Is it possible it just isn't a very good toilet design and was always marginal and didn't take much to not work at all. Hate to replace the whole toilet if it isn't necessary.

Hi izzy and Welcome to The Plumbing Page. At AskMeHelpDesk.com. If you have no jet opening in the bottom of the bowl then you have a gravity bowl. This depends on then weight of the water coming out of the tank to start the siphon action,
Check the tank level. It should be 1/2" under the top of the overflow tube. Also check to seem if water is coming out of the little tube connecting the ballcock to the overflow tube. That helps 8increase the bowl level. Let me know what you find. Good luck, Tom

Thanks. Already checked those things. I can dump a 2 gal. bucket of water in the bowl and it still goes down slow. Just realized though I have 2 overflow tubes and most toilets have one. I have a taller one at the back like a vent tube. No water in it. That's the one I plug to get the water to go down better. It's a Briggs toilet if that helps.

Figured it out! I looked at another toilet like it and there is a white plastic container thing that slides into the tank over that back tube. It must provide the air volume needed to create the siphon effect needed. I'm sure it's part of the water saving feature to cut it down to 1 gal per flush. Now I need to find a replacement plastic bottle thing. Amazing, the toilet won't flush without it.

Can you take a picture of your tank parts? Back to you. Tom