In Las Vegas, water used indoors travels a continuous loop.

From homes, water flows to a treatment plant, which sends it back to Lake Mead. Then an equivalent amount is pumped from the lake, and the 12-mile journey to treatment plants and Southern Nevada’s taps begins again.

The Southern Nevada Water Authority wants that system preserved because it allows Las Vegas to consume more than its annual 300,000-acre-foot allotment from the Colorado River. Water returned to the lake converts to credits that the Water Authority can use to pump more water from the lake.

But some homeowners, builders and environmentalists watching this continuous loop wonder: Why not shorten the distance water travels by allowing homes to keep and recycle the water they use – what’s known as graywater? Water from sinks, showers and washing machines could be reused to more efficiently and cheaply water lawns or other landscaping, they say.

Building codes in Clark County don’t allow household graywater recycling.

The water authority, after studying the idea, decided this year to make it official policy to oppose it.

The debate over how and where water recycling should occur, in a region with a diminishing supply, flared up last week in Carson City during debate on Assembly Bill 363, which would allow household graywater recycling. Beyond questions of energy efficiency and water conservation, the debate came down to the concept of property: Once a household uses water, who owns it?

“People paid for that water and I think they should be allowed to do with it what they wish,” said Launce Rake, spokesman for the Progressive Leadership Alliance of Nevada.

Rake said he supports on-site graywater recycling because it would cut down on considerable energy use for treatment plants and pumping, and save the water that gets lost in the journey to and from Lake Mead. It’s wasteful to use drinking water – a precious resource – on lawns and landscaping, he said.

Such views are part of a nationwide trend toward graywater use.

“Potable water is really highly valued water,” said Peter Gleik, president of the Pacific Institute. “You’ve spent a lot of money cleaning it up and you should use it for high-value things.”

Such a view also has a populist appeal.

As an experiment a couple of years ago, Southwest Homes President Todd Slusher reworked the pipes beneath a trailer in Pahrump and rerouted the graywater tank so that it watered a 2,000-square-foot plot of plants and grass. The trailer’s resident rarely had to pick up a hose.

Slusher figured a similar system could be a popular feature on the new homes he builds. An investment of a couple of hundred dollars could cut water bills by 60 percent to 70 percent, he estimated. It would also protect home buyers if water were to become a lot more expensive than it is now, the homebuilder said.

But the water authority contends that’s the problem. What’s the incentive for residents to curb consumption if their water bills drop? water officials argue. Even more water would be drawn from Lake Mead, without returning.

“It doesn’t help us stretch the existing allocation out of the river,” water authority spokesman Bronson Mack said.

In addition, the cleanliness of graywater is questionable, he said.

“The quality of graywater is very, very, very low,” Mack said. “Just look at the back of your shampoo bottle or what’s in laundry detergent.”

Graywater recycling proponents insist the water has been proven to be safe.

Graywater recycling is popular in some places that don’t have municipal recycling systems for potable water. Tucson, for example, will by 2010 require that new developments be plumbed to allow graywater use.

And the water authority supports residential graywater recycling in rural areas outside of Las Vegas where water doesn’t flow back to Lake Mead.

Policy in Las Vegas has moved in the opposite direction. In December the water authority board voted to approve a recycling policy that prohibits graywater systems in the Las Vegas Valley. That proposal was recommended by the Clean Water Coalition after the organization studied graywater policy in other states.

County Commissioner Chris Giunchigliani’s vote against that policy was her last as a member of the water authority board. She then promoted a state bill to allow graywater recycling.

Drafted by Assemblywoman Sheila Leslie, D-Reno, AB363 requires the state Health Board to adopt regulations allowing residential graywater recycling.

Testifying last Monday in Carson City before the Assembly Health and Human Services Committee, Giunchigliani said the bill would save water and energy, and create green jobs.

Environmentalists testified in support of the bill. Water authority representatives opposed it.

The bill wasn’t voted out of committee last week, a deadline for bills to advance, and the idea appears unlikely to proceed.

At the hearing, Assemblyman John Hambrick, R-Las Vegas, asked Sen. Terry Care, D-Las Vegas, a co-sponsor of the bill, if the use of graywater would decrease water returned to Lake Mead.

Care replied that he was interested in helping Las Vegans reduce their water bills, which is their right.