The Castlewood community is facing a significant water supply breakdown that could extend into at least Monday amid pump failures within the San Francisco Public Utilities Commission-owned well system that serves the area in unincorporated Pleasanton.

Officials with the SFPUC and Castlewood Property Owners Association are asking Castlewood residents to limit use of their household water as crews work to temporarily supplement the water system's tanks while troubleshooting of the underlying pump problem continues. The Club at Castlewood stopped water irrigation for the day.

Stop-gap strategies on Sunday have included trucking in water from SFPUC facilities in the Sunol Valley as well as trying to establish a hook-up connection to a nearby city fire hydrant to pull from the Pleasanton municipal water system, according to SFPUC press secretary Will Reisman.

"This morning, one of the two groundwater well pumps that are part of the SFPUC-owned Pleasanton well system failed. The other well failed over a month ago and a new replacement pump is on order," Reisman told the Weekly late Sunday afternoon. "This is the sole source of supply for Castlewood and these residents."

"SFPUC Water Supply and Treatment Crews have been troubleshooting the issue all day," Reisman said. "Combined, the trucks and the hydrant 'jump' will not meet the normal demand off this system, but will help."

"We will continue to troubleshoot the pump issue from multiple angles. We will have another update tomorrow morning," he added.

Approximately 280 Castlewood customers have been impacted by the water outage, according to Pamela Ott, deputy city manager for Pleasanton.

Steve Tangney, president of Castlewood POA, has been providing updates via email to homeowners in the affluent Pleasanton neighborhood and country club community off Foothill Road.

"It is important to continue to limit water usage to the absolute minimum until further notice. As mentioned earlier today, turn off all irrigation and please postpone household usage such as clothes washing and dishwashing," Tangney wrote around 4 p.m. Sunday.

As of that time, Tangney said SFPUC had trucked about 12,000 gallons of water to the agency's 200,000-gallon reservoir in the area, which was nearly empty.

"The trucking of water will continue through the night but is a slow process and will yield a very limited supply compared to normal operation such that Castlewood residents have been notified and asked to limit water usage to a minimum until further notice," Ott said.

Reisman did not elaborate on the specific problem with the well that occurred this weekend. Ott said the city had been informed it was "inoperable due to an electrical issue."