San Franciscans who want to conserve water by irrigating their yards with the runoff from their showers and bathroom sinks will no longer have to get a $250 permit or inspection from the city, under legislation introduced Tuesday by Supervisor Scott Wiener.

The legislation comes as the state suffers through a four-year drought that has prompted city officials to encourage people to save and recycle water.

“We have a structural water problem and sometimes we act as if we live in a lush tropical environment with endless water and we don’t,” Wiener said. “Whatever happens with the current drought, we need to restructure how we use water. Recycling is a key approach, so let’s make it as easy as possible.”

Small revenue loss

The city’s loss in revenue would be minimal: Since 2012, the Department of Building Inspection issued just five permits for installation of simple gray-water systems. A permit is not needed to reroute leftover water from washing machines for irrigation.

Laura Allen, co-founder of Greywater Action, an Oakland conservation group, said it makes sense to also eliminate the permitting requirement for recycling shower and bathroom sink water.

“We need to make sure the regulations are in line with the risk and the potential benefits for people reusing water,” Allen said. “When it’s such a low risk, a permit is getting in the way because of the costs and the fear of inspectors.”

A simple gray-water system can be installed in most homes for about $300, with parts bought from a hardware store, but more elaborate systems can cost anywhere from $1,000 to $20,000. Most gray water is used on gardens or for flushing toilets.

The easiest way to recycle water is to install a rain barrel capturing roof runoff — and in the Bay Area, both simple gray-water systems and rain barrels are undergoing a boom in interest.

Brent A. Helm, a civil engineer who installs gray-water systems, said interest in them has grown fourfold since last year.

“I would say I probably get five incoming calls or e-mails a day for gray-water systems,” Helm said. “A year ago, I would get maybe five a month.”

He added that many people install simple gray-water systems without getting a permit because of its cost.

“Most of the time, once the client looks at the cost of the permitting, they realize it’s a large portion of the actual cost of the total product and it dissuades them from going about the proper channels,” he said.

For evidence of how effective gray-water systems can be for slashing water usage, San Franciscans need look no further than Australia.

Gray water and rain barrels played a significant role in Australians cutting their water use in half during that country’s catastrophic 13-year drought, dubbed “The Big Dry,” that ended in 2010. Today, two-thirds of the country’s homes use gray water. About half have rain barrels.

California’s usage

By comparison, just 13 percent of California households use gray water, according to the Oasis Design environmental research group. Nationally, 7 percent of households use gray water. And rain barrels have never really caught on.

Australia gives $5,000 rebates to every home that installs a gray-water system — and that incentive program is about to ramp up even further, with this year’s El Niño predicted to kick the country into another drought while it drenches California.

In San Francisco, residents of single-family and two-unit homes can apply for a free 50-gallon rain barrel and downspout diverter kit from the San Francisco Public Utilities Commission. The program started last week and lasts through January or until the supplies last.

Greywater Action is trying to get legislators to change the state law that prevents kitchen gray water to be reused in California, but has found no sponsor. Kitchen gray water is prohibited in this state because of its high amounts of fat and food waste, and occasionally fecal coliform, but Oregon and Washington allow kitchen gray water use if it is rigorously screened.