Steiner's apartment dates back to the 1920s and leaky faucets are common. She reports these immediately to the landlord. And like many Californians, she conserves by flushing the toilet only when there's solid waste—but then she takes this practice a step farther by asking her guests to skip the flush.

"I'm pretty religious about this," Steiner said. "Most people who are regular guests here know and they don't' flush. My friend's boyfriend came over once and said 'I'm sorry to say I flushed your toilet.' This happens."

In the kitchen, Steiner takes water-saving to an even more extreme level. Pots in in the sink catch runoff, whether it's soapy water from washing hands or drips from the faucet. This gets used and reused to wash dishes. She drinks from the same glass throughout the day and only washes it once in the evening. Same goes for plates and cutlery.

Butternut squash ravioli are a favorite meal and Steiner eats a bowlful nearly every day. She'll use the same water for boiling the ravioli over several days. After her morning oatmeal, she uses recycled water to soak the dirty pot, and then draws from that water to rinse her bowl.