Thousand Oaks residents have been doing a great job conserving water, say city officials.

Even with a loss of 700,000 gallons of water in December due to a city-owned tank overflow, water consumption in the city was down more than 15 percent from the year before, said public works director Mark Watkins.

“We hit our targets . . . so far this year,” he said.

That’s a very good thing, because if Thousand Oaks water consumers, who include the city, the schools, the park district, residents and businesses, don’t reduce consumption by 15 percent compared to the previous year, a $4-million fine will be imposed on the city’s water company by the Metropolitan Water District, a regional water supplier.

That fine would be passed on to customers and could increase water bills by about 33 percent, Watkins said.

The goal of a 15 percent decrease in consumption began in July 2009 and continues until the end of the fiscal year in June.

A city water ordinance, now at Level 1, permits Thousand Oaks residents to water their lawns no more than twice a week until March. Then it increases to three times a week. Water leaks must be repaired quickly. If the city gets involved and notification goes out to fix a water leak, the repair must be made within 72 hours after notification or fines could be imposed.

Outside watering is prohibited between 9 a.m. and 5 p.m. When sprinkler systems are allowed, the duration is limited to 15 minutes per day per station with no excessive water flow or runoff permitted.

Washing hard or paved surfaces isn’t allowed, so spraying driveways, sidewalks or patios with a hose is prohibited.

Most of the city’s professional carwashes already use recirculated water and laundry systems, but the ordinance requires any new carwash to have such systems. All commercial conveyor carwashes must have them installed by 2010.

People who wash cars at home must use a self-closing shut-off nozzle at the end of the hose to prevent water from running into the street while it’s not being used to rinse the vehicle.

School carwashes must do the same. Water used in fundraisers must be reclaimed. Sandbags should be used to block the water from going into the drains or running down the street, and wet vacuums can be used to reclaim it for uses such as watering landscaping, Watkins said.

The city has a hotline for residents to report others who use water excessively: A recording at (805) 375-5747 can be used.

Those who don’t obey the ordinance can be fined $100 for the first violation, $200 for the second violation within the same year and $500 for each additional violation that year.

The city’s need to preserve water comes from an ongoing drought and environmental concerns for the small delta smelt fish. The desire to protect the fish has restricted the transportation of water to Southern California from the Sacramento-San Joaquin Delta.

Local restaurants now only serve water to patrons who request it. Hotels must give guests the option to decline fresh linens each day.

These and other water conservation restrictions are making a difference, Watkins said.

Mother Nature has also helped recently.