Thousands of Delawareans waste millions of gallons of drinking water every year by over-watering their lawns or being careless with taps and appliances.

Tom Hubbard, public relations manager at United Water, said the company uses drinking water week, held annually from May 4 through May 10, to educate people about conserving water.

He said water use in New Castle County, where United Water supplies drinking water to 110,000 people, can increase by 50 percent during the Summer.

Most of the increase is caused by people watering their lawns, but Hubbard said if people understood how their lawns should be watered, the increase would not be as dramatic.

To help people conserve water, Hubbard said United Water started publishing an EvapoTranspiration Index that tells people how many minutes a day they need to water their lawns.

The index’s name is a combination of evaporation, which is water absorbed from soil into the atmosphere, and transpiration, which is water absorbed by plants, said Hubbard.

The EvapoTranspiration Index uses temperature, wind speed, humidity and other environmental factors to calculate the number of minutes everyday from May through September, he said.

The soil in Delaware will hold water for four days, so people should check the index every four days to see how long they should water their lawns, he said.

Conserving water is especially important during the Summer because of the way drought affects the water supply, said Hubbard.

United Water pumps about 22 million gallons of water a day from the Red and White Clay Creeks, but during mid-August, when creek levels are low, demand for water is about 27 million gallons a day, he said.

He said because New Castle County received so much precipitation during Winter, the creeks have rebounded from any droughts last Summer and there should be plenty of water, but conservation is still important.

Droughts have less of an affect on the underground aquifers Artesian Water uses as its water sources, said Joseph DiNunzio, executive vice president of Artesian Water.

The company delivered more than 7 billion gallons of water to 250,000 people last year, but DiNunzio said people overuse tap water because they take it for granted.

There are dozens of simple things people can do to conserve water, like turning off the taps when they shave or checking their toilets for leaks, he said. A toilet is the largest water user inside a home and an undetected leak can waste hundreds of gallons of water, said DiNunzio.

He said clean drinking water is too valuable a resource to be wasted. About 3 million people die of waterborne diseases each year, but the water-treatment systems used in the United States keep millions of people safe, he said.

All the water Artesian pumps is treated with chlorine to prevent contamination, treated with fluoride to promote dental health and carefully monitored to ensure it is not too acidic, he said.

Preserving the quality of drinking water is vital to individuals, businesses and firefighters, which is why people need to keep pollution out of the water supply, he said.

When people flush pharmaceuticals down the toilet or pour oil and gasoline down the drain, they could be contaminating their only source of clean drinking water, said DiNunzio. One gallon of oil can contaminate one million gallons of drinking water, according to the U.S. Environmental Protection Agency.

Over-watering lawns also contributes to pollution because excess water runs off the grass and could carry lawn chemicals into the water supply, Hubbard said.

It may seem like there is an unlimited supply of water when you turn on the tap, but Hubbard said groundwater is a scarce resource that everyone needs to preserve and conserve.