The limestone could be crush tested for strength.

The urbanite will slowly deteriorate and (good) limestone will deteriorate much slower and will simply weather on the surface a bit while the concrete will eventually crumble away.

The cracks might be layers of weaker stone between good hard layers (now that is just pure specualtion on my part).

I just can't bear to see a lot of limestone go unused! It would have to be pretty bad to be weaker than concrete. The cracking idea is a new one for me, but if you have a conversation with a stone expert they may be able to tell you all about it.

I am with you on the gravity drain. It will only leak with a pump if the power goes out.....and the power WILL go out sooner or later, and if you are out in the boonies it will probably go out sooner.

Tom W

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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.