I do know that it is 1980's technology and it empties into a creek bed that's only running in water half the year. Never seen anything come out other than clear water...
That's how my grandparents was, pipe came out of the ground down below their place, water ran into the creek. My parents have a holding tank, then a perferated tank, then leeches into the ditch crosses under the road a fertilizes the field across.
I don't know what we have, house is 100+ yrs old. Heard the bathroom was put in in '63. See no evidence of what it is or where, hopefully I have no problems. Doesn't stink anywhere, front yard dry. You shouldn't have to have a tank pumped, if it's working properly, breaking down solids. Adding those bacteria tabs is a good idea. You can also add sour milk down your drain, works the same. Grease should not end up down the drain. Toilet paper would be best if it wasn't flushed but I don't know many that wouldn't (Gramma wouldn't).
Best setup, how our house is, only toilet water goes to tank, all other drains (grey water?) go directly to leach field, or elsewhere all together. That way soaps, detergents, bleach, etc doesn't affect or harm the bacteria breaking down the solids in the tank.
Buddy of mine built what he called a evaporation field. Perferations in the pipes goes up rather than down as in a leach field. Sets on a thick layer of gravel with grass growing on it. Don't know how it worked out haven't been there in a long time. The reason he said he was going to try it was he's never seen a leach field work right anyway, they always leak out somewhere and stink.