Standing water in sewer... without clog?

[Baldrick]

It's a mystery for my family for over couple months now but discovery couple days ago narrowed down to what the problem could be.

1. There is water standing in the sewer pipe.
2. Septic system has been pumped and water table is low in the tank. It's about 60ft from the house.
3. With moderate usage, sewer pipe fills up all the way to the point where it floods the basement floor through the floor drains.
4. Gurgling in one of the traps indicates the moment when water level passes that branch when filling up, then again gurgling when it comes back.
5. IMPORTANT - 2 days ago noticed big pool of water by the end of drain tile outside. It was about 0F outside and stinky water was still coming out.
6. About 5 days ago, sulphuric acid drain cleaner was dumped into the floor drain, followed by gallon of water (possible connection to #5?)
7. Drain has been snaked 2x now and confirmed that snake ball hits the metal baffle in the septic tank. Very little water goes in the tank.
8. Drain tile runs by the basement floor (about 7ft under ground) and crosses the septic pipe (never seen the pipe, must be below the drain tile)
9. Septic system is circa 1983, assuming it's PVC.
10. There are several big black walnut trees growing around the septic.

I called some plumbers with drain cameras but still waiting to confirm the appointment. They would like to see clear pipe (no crappy water) when running it, but obviously that might be not possible.

What possibly could be the cause?
1. Would S-trapped (collapsed) pipe cause my problem?
2. Separation in pipe (so top edge of incoming part sits just above the bottom edge of following pipe)
3. Tree roots (but then snake passed through and water is still not draining)

Any other ideas or suggestions?
Does it make sense to rent power auger and try to clean it myself before plumber shows up?

[jadnashua]

What size snake head did you use? Ideally, one the ID of the pipe with a cutter head. There should be no standing water in the pipe. There are only three reasons I can think of that would cause that: a collapsed pipe, or a belly, or a clog. The clog may not be total, and when some toilet paper or whatnot catches on what's there, it temporarily either slows things or clogs it momentarily. Unless the pipe isn't buried below the frost line, it should not get clogged from freezing. But, we've been having some quite cold weather, and the 'normal' frost line maybe inadequate. Usually, though, the local requirement takes this into account. A power auger in an inexperienced user's hands could lead to the loss of a finger or two, or worse. It is a powerful, dangerous piece of equipment.

[Terry]

Does it make sense to rent power auger and try to clean it myself before plumber shows up?

I've run one before, and they are scarey as heck!
I broke the watch on my left wrist when the cable wrapped me up. One of the guys at work has the tendon to his thump snapped.
I don't own a snake now for those larger pipe sizes.

It's a back up of some sort though. Normally you don't want to put anything down a septic that isn't organic though. It's like a living thing, and you don't want to mess with that.

[Baldrick]

I used ~$35 snake with about 1-1/4" ball type head. Didn't think about possibility that whatever hole was punched through could plug up right when I coiled it back. Good point.

Doubt the line froze, it's good 7 feet under ground.
Also, gave up on renting power auger. If pipe is separated and shifted, it won't do any good. I see that as the most likely culprit. Coming water dumps below the bottom of the next section. Accumulated crap prolly got washed off the snake ball since entire pipe is full of water. Otherwise how the #2 gets past that point?

Managed to schedule the plumber for tomorrow and he will have camera, power auger and jetter with him. Just hoping it won't cost more than couple hundred $$.
Hate spending money on stuff like that, but in this case I see no other choice.

[hj]

Your diagnosis and descsription do not jibe. IF the tank has little water in it, and IF there is no stoppage, regardless of any "dip" in the line, the water WILL flow into the tank. You have a problem, but nothing you have posted gives any indication of what, or where, it is.

[Baldrick]

Sewer pipe was crushed outside, had about 5in hole and was filled with gravel from surrounding drain tile installation.
I guess my 1" snake head was able to punch through, but much bigger auger that plumber brought couldn't, just like his camera.

Long story short, it turned out that I know the plumber from previous jobs (running his own business now) and it cost me $100 to establish that it has mud inside (by power augering and running camera that didn't really show us anything) and then $400 to excavate it, replace ~2ft section of sewer pipe, backfill with gravel (it was right below drain tile) and fill the hole.

Cheapest/best possible scenario if you ask me and everything works perfect now.