Locating a septic tank and clearing a clogged root bound sewer line

We purchased this property in September and the only plumbing running to the septic (built in 1974) was the toilet and bathroom sink (the shower was not yet functioning, and the kitchen sink has a seperate grey water line). Because it was getting relatively little use (we were only there on weekends), we didn't notice things were clogged until 3 months later when we got the shower working and it backed up on the first use.

I was unable to clear the blockage from the cleanout using a sewer rod, so I had to locate the concrete septic tank in the yard. I tried to locate it with a piece of rebar, but the ground is full of field stones, so it was hard to tell whether I was hitting rock or cement.

Eventually, I just dug holes and followed the line coming from the house until I found the tank. Upon opening the tank I found the outlet was very root bound. Fortunately, the main clog was close enough to the outlet that I was able to work through it, releasing a deluge of backed up sludge. I'm pretty sure none of the solid waste had been making it to the tank since we purchased the property, and possibly even before then (it had not been inhabited full time for many years before we bought it).

Later after the line was cleared, we ran a camera up the line and learned the thin walled pipe was in bad shape due to cracks/root infiltration. We've since replaced the end section of pipe with a temporary "patch" of pipe and will be soon digging up the entire line from the house and replacing it with schedule 40 pvc.

On the plus side, the cement tank and baffle all look to be in good shape. When we measured the sludge level on the bottom of the tank, it was less than 2'. There was little to no scum layer on top, which I'm thinking is the case because it had not been receiving soap/grease/etc. in many years.