My cleanout extends about three ft out of the ground between the house and the septic tank. I have standing water up to about six inches of the top of the cleanout. We had the tank pumped about 2 years ago (there are two of us living in a house built in 1994). We also have a septic alarm that tests okay, but has not gone off. Does it sound like the line is plugged between the cleanout and the septic tank (there should not be any tree root problems).

What prompted you to open up the cleanout? It does sound like a blockage exists in the line, possibly something flushed down.