Some facts:

Bought this house recently. Problem has been there since the beginning.

- Toilet bowl would try to fill but empty then gurgle when it reached as low as it could go.
- When flushed, water would rush into the bowl from the lower jet but would not flush down the drain.
- I decided to replace the toilet with an American Standard Cadet3 1.28 gallon chair height and it is still doing the same thing

- I poured a 5 gal bucket of water down the old toilet before removing the old one and it flushes really well that way.
- When I pulled the old toilet there was standing water in the line about 2-3" below the flange.

- Last night my master toilet on the same level got clogged and this caused the problem toilet to clog as well (same drain line). I used a plunger on the master toilet and the water in the problem toilet bowl went down as well.

- My master toilet flushes and fills the bowl fine.
- I went on the roof with a hose and poured water down the vent stack, it went down fine.


What is going on here? Is the plumbing wrong?
I don't think there should be standing water in the drain line.

Here is the video : [www.youtube.com]



Edited 4 times.

I bought a 25' Esdoscope to look down the vent stack.
I'll do that today.

WHY? You already know the problem, it is the water in the pipe under the floor. You have to find out WHY the water is there before you waste even more money, on useless remedies, such as replacing the toilet.

Yes but I cannot make a sense of it.

Here is a video I took with an endoscope,
15 ft below the vent stack, about where this problem toilet is: [www.youtube.com]

There is standing water in the vent, so I will try snaking it from the roof tomorrow.

Is there anything else I should be doing? I poured boiling hot water down the toilet and it did not help.

how old is the house?
what type of pipe material is used under the floor?
are you able to see underneath this pipe? is it leaking?

I suspect your pipe is damaged, leaking liquids and leaving solids behind , and as a result: clogged.

UPDATE:


[www.youtube.com]

I pulled the toilet (which i hate by the way American Standard 1.28 gallon Cadet 3 = will be returning this junk)

Anyway I snaked the line and cleared it, although it did not feel like a terrible clog, one or two forward motions and it was clear.

Get this, there is a trap in the waste line, and I think the toilet cannot flush fast enough because of this.
I still have standing water there.

I need to rip down walls to remove the trap but that's after I hit the lottery.