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San Francisco Turns to Graywater, Alternate Sources in New Construction to Conserve Potable Water

In the midst of a costly drought gripping California, San Francisco has an eye on the future for water conservation efforts.

The San Francisco Board of Supervisors recently passed an ordinance mandating water recycling and conservation measures for large buildings.

Buildings more than 250,000 square feet will be required to maintain alternate water sources such as graywater for toilet flushing and irrigation.

Instead of using potable water to wash sidewalks, water plants and get rid of waste, new developments are encouraged to use graywater, or untreated wastewater that has not been in contact with any harmful contaminants. This includes wastewater from showers, bathtubs and washing machines.

While the water is not safe for consumption, it can be used for other purposes in place of potable drinking water.

Using graywater was once banned in California, but the historic drought has shed the stigma against using second-hand water.

"We need to stop using pristine drinking water to flush our toilets and to do landscaping," San Francisco Supervisor Scott Wiener told the local National Public Radio Station, KQED. "We are in a crisis and we need to act like we're in a crisis."

Under the new ordinance, large buildings will be required to use alternate water sources for 100 percent of the water demanded for toilet flushing and irrigation. If there is not enough rainwater or graywater available, the development must then turn to blackwater, stormwater or foundation drainage.

Unlike graywater, blackwater is derived from toilets, sinks and dishwashers and contains bodily or other biological waste.

Buildings smaller than 250,000 square feet but larger than 40,000 square feet will also face new water regulations.

Small developments will be required to assess the amount of rainwater, graywater and foundation drainage produced on site in the hopes of reducing the use of potable water. However, they will not be required to install alternative water systems at this time.

The committee also proposed that within five years, only non-potable water is to be used for the purpose of irrigating and cleaning public parks and other public spaces. Within the next two years, city officials will research the costs and other factors involved in fully enacting such a rule.

San Francisco residents are even encouraged to install graywater systems at their homes. The San Francisco Public Utilities Commission offers rebates to some graywater installations and has a laundry-to-landscape program set to launch this fall.