T., you're thinking of a septic tank ~ it's designed to ferment and break down the solids and usually has "leaching" pipes radiating out from it that have holes along their bottom part so as to allow the liquid to seem out and settle .

(lord I worked on/in/with and installed a lot of those in rural New England in the 1960's.... ) .

Old dry wells were often concrete, brick or rock lined then filled with large stones, only ground water run off was allowed to go in , no sewage .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

No, I know what a septic tank is. These dry wells took the place of a finger system. You could use them for other water too if you wanted I suppose.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I'd be leery of collapse, just like occurred at my old house .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

If not maintained, possible.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

That's the entire point : after whomever dug and installed an empty dry well moves on, no one else will know its there and unless it's a nice Concrete one with a cap like you described, it's simply a matter of time before it fails.....

Why I was taught to never build them empty ~ fill with large stones or something .

Only rich folks could afford those fancy-schmancy Concrete things .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better