My ex-wife bought a place like that. She called me one day to find out why her septic had failed and I told her to call a pumping service. It turns out the “septic tank” was a 55 gallon drum and a pipe that went right to the Yakima River.
Being a Civil Engineer I have seen these home made jobs everywhere and just shake my head. It’s like the old FRAM oil filter commercial, you can pay me now or pay me later, but you can’t use your toilet until it’s fixed!
Neighbors years ago used a car as a septic tank.