In my former farmhouse in Iowa, I had an old cistern attached via piping directly to the house. The house also had a concrete underground chamber with a large metal tank with a water drip mechanism at the top. Calcium carbide was placed into the tank and, when dampened, the resulting acetylene gas was piped into the gas light fixtures in the house. Unfortunately, essentially all the gas fixtures had been removed. The cistern had been capped years before I acquired the place, but I removed the cap and installed a hand-operated pump which worked great for pumping up water for non-drinking use. In the course of uncapping the cistern, I inspected it carefully (it was about half full of water presumably just from seepage from small cracks) and saw the skeleton of a snake in the bottom. Since I wasn't using the water for drinking, that wasn't of great concern to me. Originally, the cistern was filled by run-off from the farmhouse roof. I wish I still had that house, but sold it before moving to the west coast.