Hamptons estates dominate the list of Suffolk's biggest residential water users, a trend that is straining water infrastructure and contributing to concern over saltwater contamination.

The Southampton estate of billionaire David Koch tops the list. Last year, his 4-acre property consumed 20.7 million gallons, data from the Suffolk County Water Authority show.

That's more than 100 times the amount -- 160,000 gallons -- tapped annually by the typical county homeowner.

Among the other top residential users last year were several business and banking titans: J. Crew chief executive Millard Drexler's Bridgehampton home ranked second, consuming 11.5 million gallons; record and movie magnate David Geffen's East Hampton estate ranked ninth; and fashion designer Calvin Klein's Southampton home was 28th.

Koch has been the county's heaviest water user for four years. Of Suffolk's top 50 residential users in 2014, all but four were in the towns of Southampton and East Hampton. Nine were on Koch's street, Meadow Lane, an oceanfront strip that is one of the country's most exclusive enclaves.

Heavy usage in the Hamptons, residents and officials said, is linked most often to the irrigation of expansive lawns and occasionally to geothermal heating and cooling systems. The consumption has contributed to water main breaks and a need for additional wells, county and local officials said.

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Water authority chairman James Gaughran said in an interview that his board has commissioned a study to determine whether the heaviest water users are a factor in increased infrastructure costs and should be charged higher rates.

"It does make it difficult during the height of the summer months to make sure everything is working properly," Gaughran said. "Our people have to rush out to repair water main breaks when peak demand creates water main breaks, but we're always able to deliver the water."

Drilling to meet demandThe Suffolk water authority, which serves about 1.2 million people in the county, has drilled six new wells on the South Fork and has increased capacity on several existing wells since 2010 to keep up with demand, said spokesman Tim Motz. Officials plan to drill two additional wells in Southampton and one in East Hampton this winter, said Joe Pokorny, the authority's deputy chief executive for operations.

"We build new wells all over the county, because demand does change throughout the whole county," Pokorny said. "The area where the largest growth is going on is pretty much the South Fork."

The amount of water used for lawn irrigation has risen sharply in recent years, straining the infrastructure on hot summer days, county officials said in a March report on Suffolk's water resources.

"If the trend of increasing summer irrigation continues, stress on the existing infrastructure will also increase," the report said, stating later that "landscape irrigation practices and seasonal population increases on the East End have a significant impact."

Southampton Village administrator Stephen Funsch said he met with water authority officials two years ago to urge them to drill more wells in the village. He said that, at the time, Southampton Hospital was losing water pressure on its third floor during periods of peak water usage in the village.

Heavy water usage has also caused saltwater to seep into drinking water in some parts of Long Island with shallow aquifers, such as Montauk, Pokorny said. He added that the water authority monitors those areas and controls pumping to prevent saltwater contamination.

Suffolk officials said the underground aquifer that supplies water to county residents is in no danger of running out. But Adrienne Esposito, director of Citizens Campaign for the Environment, said saltwater contamination is a growing concern on the South Fork.

"These water hogs need to have an incentive to conserve water," Esposito said. "They're actually doing damage to the entire South Fork aquifer system."

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Several independent authorities exist apart from Suffolk's water authority and are not included in the county's data: South Huntington, Dix Hills, Greenlawn, Riverhead and Hampton Bays. Private wells are also not included in the county's figures.

Suffolk's March report said the average amount of water pumped each day in the county rose by 56 percent between 1980 and 2013, while the population only increased 14 percent, a trend county officials attributed to the use of automatic sprinklers. The report recommends that county officials adopt regulations within three years to manage residential and commercial irrigation.

Koch water bill: $34.5GKoch, who co-owns Kansas-based Koch Industries Inc. with his brother, Charles, is worth an estimated $41 billion. He is the fifth-richest person in the country, according to Forbes. His estate has a tennis court, swimming pool and an energy-efficient geothermal heating and cooling system.

A Koch spokeswoman attributed the estate's heavy water usage to the system, which pipes water through the earth and relies on the earth's stable temperature to heat and cool a home. It requires some electricity to operate, but is considered more environmentally clean and energy-efficient than oil or gas systems.

Koch and his family use the 12,000-square-foot house year-round, though it is not their primary residence, the spokeswoman added. Koch's bill for the estate's 2014 water usage topped $34,500, based on a rate of $1.67 per 1,000 gallons provided by the water authority.

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A Calvin Klein spokesman said Klein's water usage should decrease as water-efficient landscaping takes root.

"All the seeds of everything they planted on the property are low-water users," said the spokesman, Paul Wilmot. "The thing is, they need two years to be acclimated."

Wilmot noted that the Meadow Lane property spans 10 acres and that landscaping is an important part of its allure.

"The quality of all these houses and the unusual appeal, a big part of it is the landscaping," he said. "And guess what it's on? Sand. It's the most porous thing in the world."

J. Crew representatives did not return emails seeking comment. A Geffen spokesman could not be reached for comment.