When I read that they were using 299,221 gallons of water, I assumed that they lived on some giant estate. But if you look at the picture of their home, it is a smallish, modest house. Sort of a lot of lawn, but not really.
Unless they have a huge backyard, it sounds like they were pouring water onto their lawn *far* in excess of what it actually needed. (BOTE and a little guesswork yields 10gal/sqft/mo, which is a *lot* of water.)
"I may be synthetic, but I'm not stupid" -- the artificial person, from _Aliens_