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DENVER — An ambitious plan could be on the horizon for Denver Water customers. The public utility says it wants to replace tens of thousands of service lines to ensure water will be lead-free in every home, business and school throughout its system.

The project could cost up to $500 million.

Denver Water insists that the water it delivers is already lead-free. However, after water leaves that main service line, lead can leach into drinking water through individual home service lines or via internal plumbing.

In Denver, officials said their worry is with older homes built before 1951. Prior to 1951, lead was the preferable product for home builders.

“Those lead service lines are the main cause of concern,” said Travis Thompson with Denver Water.

Lead increases the risk of serious health issues, including cancer.

Denver Water serves about 1.4 million people in the city of Denver and some of its suburbs.

There are anywhere from 50,000 to 90,000 lead service lines connected to the Denver Water system. Crews replace about 1,200 of those lines during annual construction projects, according to the utility. Denver Water says it’s time to be more aggressive with the replacement work. The utility’s plan does not include replacing plumbing in crawlspaces or basements. The proposal offers replacement of service lines that typically run from the street to a house.

Denver Water must receive approval from federal and state government officials before its plan becomes a reality.

Denver Water wants to perform the replacements at no cost to the individual homeowner. Instead, water rates are projected to increase to cover what could cost up to $500 million over the next 15 years.

“If you live in an older home, get a water quality test to determine if you have any of these risks in your home,” Thompson said.

Water quality tests — provided by Denver Water — come in a box with three water bottles. Customers are expected to fill the water bottles using their kitchen sink or a bathroom sink. Following detailed test instructions is key to determining if lead is coming from your faucet, internal plumbing and/or the service line.

The tests can be ordered online.

If the water test results come back above EPA standards for lead — at 15 parts per billion — customers could replace lead plumbing. Or, a cheaper option is to use water filters that are designed to remove lead.