Jim,
Look for a cistern [in ground tank next to house to collect rain water from roof].
Might also ask the neighbors if Gramps gave them signs for their pits.
db

Reproduction/Fantasy Cans
http://i124.photobucket.com/albums/p2/oldegaspump/AllCansMASTERTHUMBNAIL_zps4bfdbbc7.jpg
Rnd Can Re-lids