The closure prompted a major call to conserve water for residents in south Ventura and west Los Angeles counties.
Officials said it was residents' efforts that helped the plant reopen a day sooner than expected.
"We greatly appreciate the support from residents and businesses throughout the affected areas whose conservation efforts were instrumental in maintaining adequate supplies for the area," Debra C. Man, Metropolitan assistant general manager and chief operating officer, said in a statement.
Man said physical modifications were made to the district's local distribution system so that water supplies from the Colorado River can be delivered as summer approaches.
