LOS ANGELES—A group of Mulholland Drive property owners is suing the city of Los Angeles and the Department of Water and Power after their homes were flooded earlier this year when a hydrant hit by a U.S. Postal Service truck caused millions of gallons of water to escape before the pressure was turned off.

The plaintiffs in the Los Angeles Superior Court lawsuit are Jack Lippman, Darcy Demoss, Philip Demuth, Julia Demuth, Michael Jay Berger and Steven Kapelov. The suit alleges inverse condemnation, dangerous condition of public property, negligence, trespass and nuisance. They seek unspecified damages, including compensation for property damage.

A representative for the City Attorney’s Office did not immediately reply to a request for comment on the suit brought Thursday.

According to the complaint, on Feb. 13 the DWP “negligently allowed and/or caused” an antiquated, poorly serviced and maintained fire hydrant in the 7500 block of Mulholland Drive to discharge millions of gallons for more than an hour after it was struck by the Postal Service vehicle.

Three of the homes suffering flooding and erosion were on Mulholland and the fourth on Sunnywind Lane, according to the suit, which additionally states that firefighters were not able to immediately shut the water pressure off due to the hydrant’s poor maintenance.

The DWP failed to properly inspect, service, repair and update the hydrant, which was a “substantial factor” in causing the flooding and resulting home damage, the suit alleges.

The hydrant’s pipes and valves were so old and rusted that a rapid shutoff was not possible, the suit states.

In addition to property damage, the plaintiffs have suffered economic losses and emotional distress, the suit alleges.