Apparently, when this house was built many many moons ago, the first owners installed a septic tank and what's called a "dry well" which is an awful lot like another septic tank. The "special sauce" goes into the septic, then the "solids" filter down and the "watery stuff" goes into the dry well. The dry well is a a 5 sided cement tank (no bottom) that is surrounded by gravel, rocks (sometimes hay?? apparently) that has slits on the the sides. The water will sort of filter out of the dry well out the bottom and the slits. When it becomes clogged (by years of soap, oil, etc..) it ceases to drain (or leech) out- or drains out so slowly that it can't keep up with the septic tank.
Frequent pumping will help extend the life of your dry well. But according to my research, it should last somewhere around 15 to 20 years. Mine is now 35. Sometimes there is a drain field after the dry well. The drain field also filters the waste as it exits the septic. Sometimes people only have a septic and drain field. A dry well was often installed to save money or for small water usage people . Since the first owners were an elderly couple that makes total sense to me. Also, my dry well was installed (35 years ago) too deep. Or, when the former owners built the garage- they graded the area and filled in to deep. Either way- it was too deep to work correctly. It was also built to closely to a large tree, and it was built in the shade. Both of those things are wrong, and will contribute to the life expectancy of the system.
After talking to the neighbors- seems they needed new septics and drainfields too.... our closest neighbor (and her rental property) had the new systems installed a few years ago and our homes were built pretty close to each other in the 70's. She joked to me this morning she needed a scuba suit in her basement because so much sewage kept coming up. Thank God that didn't happen to us. Maybe these systems were installed by the same people- who knows. I don't have that information anymore- and the first owners have been dead for a long, long time.
SO- the septic tank itself is fine. We will find out from the health department (who is in charge of these things) if we install a new properly installed dry well, or if we need a new, properly installed drain field. OR BOTH.
It's not a total worst case scenario. It happened at a good time. (if that's possible) We have employed a good company. We can still actually use our house- our bathrooms, our sinks. It has ceased to back up. It doesn't affect my life much right now at all. And, in the end we will have a septic and leeching system installed correctly, that works correctly and a new, flat yard to plant grass on. There's my silver lining!