Maybe one day our kids will look back at us and say, "can you believe they just piped their rainwater straight into the sewer?"
These days, rainwater catchment is the latest big thing in environmental circles. Most houses just let rain wash down the roof, into the gutter, then into the street and the sewers. But with a catchment system, you can store that water in barrels and then re-use it for watering the garden.
The San Francisco Department of Public works loves the technology, since it reduces demand for water and strain on the sewage systems. A few times a year, during heavy rainfall, the City's sewage treatment plants get so backed up they overflow, sending raw sewage into the bay and occasionally into the streets.
In fact, the PUC loves it so much, it's holding workshops to teach homeowners how to build their own.
The only catch is the PUC needs some volunteer sites where they can conduct the demonstration. Volunteer to host a workshop, and they'll let you keep the rainwater catchment equipment that they build on your property.
And if you're feeling particularly ecological, you might look into recycling more than just rainwater. One ambitious home in the Sunset uses biodegradable detergent so that they can filter their laundry water through the garden.