About 50,000 gallons of Petaluma drinking water are being trucked out of town each day for some other purpose -#8212; agriculture, construction, filling swimming pools. And with the drought quickly becoming a top priority, city officials are looking into that long-standing practice.

The water being transported outside city limits is just a figurative drop in the bucket, Public Works Director Dan St. John said, but every drop counts during such a significant dry spell.

St. John revealed the little-known practice during a City Council workshop on water issues last week. It raises equity issues for Petaluma customers and potential legal complications since city rate-payers are essentially subsidizing users outside the system.

The discussion comes amid a statewide "drought emergency" declared Friday by Gov. Jerry Brown. State reservoirs are critically low and cities across the state have already begun water-rationing measures.

St. John said there are perhaps a dozen "load accounts" with the city, which pay a rate similar to residential users, plus a monthly charge for the hydrant use. It has been common practice to allow these users to load up trucks with city water for use at construction sites, primarily within town.

After a little investigation, it became apparent that some of the users were hauling water outside city limits for a variety of uses, some unknown, others for ag irrigation or livestock.

"They pay for it, but it was never intended, on the city's part, that it would be used for something like this," Councilman Mike Healy said.

It's not clear exactly who uses the water, because at least one user resells it, St. John said.

"We heard anecdotes that one was trucking it as far as Tomales, but that's unsubstantiated," he said. "We're thinking it's mostly around the west and south county."

The use amounts to less than 1 percent of Petaluma's water demand, about $10,000 a year.

"It's not going to put us over a precipice," St. John said. At the same time, "it's not nothing."

More important may be policy and legal issues.

The city's urban growth boundary and general plan have rules that restrict extending water service outside the city. City Attorney Eric Danly said there also may be implications involving the Local Agency Formation Commission, which regulates the boundaries of cities and special districts in Sonoma County.

The city could simply shut off the tap for the load account holders, but St. John said they may rely on it and believe they have been playing by the rules. Or a contract could be developed with higher rates for existing outside users.

For Councilwoman Teresa Barrett, the idea of outside users benefiting from the infrastructure that city rate-payers support doesn't sit well. She was also uncomfortable with not knowing what Petaluma water is being used for.

Healy, long a proponent of selling the city's recycled water, suggested the users may be able to buy the treated wastewater, which is approved for use on crops, vineyards and most ag uses.

"I understand you can't shut the spigot off if that's what they've been relying on, especially if it's a potable water source for them or their livestock," City Manager John Brown said. "Ultimately, we have rules about who we serve out of the area. We've got to get square with that."