The Dublin San Ramon Services District is asking residents to report a recurring problem that could jeopardize the drinking water supply.
Tapping a yellow fire hydrant without a meter in between the hose and hydrant can contaminate public water. While many businesses properly tap into the agency's hydrants, such as contractors using recycled water for a construction project, people have been observed connecting a garden hose directly to a hydrant to fill a water truck illegally.
"The risk of backflow into the public water supply is very real," DSRSD spokeswoman Renee Olsen said. "The meters we issue have a backflow prevention device built in and that prevents the problem. But if someone figures out how to couple a garden hose to a hydrant, water can wash into the hose and back into the hydrant and get into the water supply."
Olsen added the risk is caused by pressure differences that will cause water to go between the hydrant and hose, which can contain dirt and bacteria.
DSRSD provides water service to Dublin and parts of San Ramon and wastewater treatment to Pleasanton by contract. The city of Pleasanton manages its own potable water hydrants.
Leonard Olive, the city of Pleasanton's assistant director of operations services, said he wasn't aware of any recent instances of hydrants being tapped in this manner, but if it did happen, the city would immediately investigate the matter with the help of the police.
"We look down on any activity that could jeopardize the health and safety of our citizens, but we're not getting that kind of behavior out of our customers," Olive said.
DSRSD manages more than 3,200 yellow hydrants for fire protection in Dublin, the Dougherty Valley area of San Ramon and on a stretch of Camino Tassajara in unincorporated Contra Costa County.
Between 2014 and 2015, there were eight verified incidents where an illegal hydrant connection occurred with a district hydrant, according to Olsen. There have been several more during that time frame and this year that DSRSD hasn't been able to verify.
"It's not happening all the time, but often enough that we want to get the word out and get it stopped," she said.
Individuals who connect to potable water hydrants illegally can incur fines of $1,000 or more for a first offense.
Officials recommend that residents who see illegal hookups occurring call the water agency and the local police department's non-emergency line.
For Pleasanton, the number is 931-5100. Residents should tell the dispatcher they are witnessing a water theft in progress and ask if they can send an officer to investigate immediately, but callers should not confront the person using the hydrant.