Hello. I recently purchased a home, which the house itself is only 2 years old, but was built on the original 1950's slab when the original home burnt down 3 years ago. The original home was a single story ranch and the current is a 2 story colonial. I am under the impression the original pipes in the slab are still in use. 3 days after our closing, we began having issues with the downstairs toilet and bathtub, with water backing up into both after running the kitchen sink for an extended period. We had not had a septic inspection done as the tank and system were only 9 months, which I don't think the inspection would have helped anyway. After some advice, I decided to dig up the cap for the tank and check the sludge level just to ease my mind. The sludge level indicated the tank should be pumped, and I called a family friend to come pump the tank the next day. He pumped it, but then asked me to dig up the inlet inspection cover, where we found the inlet pipe to be pointed up at about a 25 degree angle. I was sure I had an issue with the main drain from the house, so we dug from the tank back and found all of the brand new pipes were not glued together and falling apart. What was strange was there a 3 inch line coming from the house(which I just found out is the dedicated line from the upstairs bathroom) and a 4 inch line(found to be the downstairs drain) coming into a Tee, and the 4 inch line comes from away from the house(see photos). We put everything back together and thought all was good and the problem was a valley in the piping. 2 weeks later, were having the same issues with water backing up. I removed the downstairs toilet and tried snaking it, can't get the snake more than 15 feet down the line. My issue is that I have no idea where the main line (4 inch) comes out of the house, the town has no records either. Im at my wits end with this. My guess is the original septic tank was directly behind the house and the main line came out between the bathroom and kitchen(see photos) and when the new tank was installed, the ex-homeowner just put a 90 degree in the old pipe and ran new to the tee with the upstairs drain to eliminate ripping up the deck, and that's where my clog is . Any help here as to where I can guess my main line is and any advice you can give me before I start digging and tracing that line back to the house? Any help is greatly apprectiated. Sorry for the long post, but the photos below show the pipes in the ground to the septic, the kitchen, bathroom, deck, backyard, and wall between the kitchen and bathroom where I think the main drain may exit. Also shown is the vent for the upstairs drain. Thanks again! 4645046451464524645346454

That is some interesting pipework there, you could have pipes backed up from rootes, you could have an absorption trench that just doesn't work because they didn't dig a new one and I don't think that digger is helping, ever thought of digging trenches by hand. You are goint to have to follow some of those pipes and establish where they come from and where they go. Maybe you just covert that tank to pump out and forget some of the hassle