Next up on President Trump’s renovation tour of Washington, D.C.: the Lincoln Memorial reflecting pool, which he called “filthy” and “dirty” and in need of a major upgrade.

Mr. Trump said on Thursday that the project was already underway to renovate the reflecting pool, which is more than 2,000 feet long and has been the site of many historic events, including Martin Luther King Jr.’s “I Have a Dream” speech.

The president said he would be using a contractor he knows from his years in real estate.

“Over the years as a developer, I’ve probably built more than 100 swimming pools,” the president said, adding, “I have some really good pool builders.”

Speaking during an event in the Oval Office about health care, Mr. Trump detoured into one of his favorite topics: construction.

“It’s filthy, dirty — the water’s disgusting looking,” Mr. Trump recalled a friend telling him. “It’s not representative of the country.”

Mr. Trump said he went to inspect the reflecting pool with members of the U.S. Secret Service and Doug Burgum, the interior secretary. He said one contractor proposed removing the pool’s granite and replacing it with stone as part of a three-year renovation that would cost $300 million.

“I said, ‘No, there’s a better way of doing it,’” Mr. Trump recalled. “I said, ‘What we’re going to do is I’m going to call all three of these people that have worked for me in the past doing swimming pools.” He said he told the contractors to “give me a good price,” and one agreed to do the job for $1.5 million to $2 million.

He said the contractor began work two weeks ago and has “scrubbed” the surface of the pool.

“Now we have a nice, clean surface on which we’re putting an industrial grade swimming pool topping,” Mr. Trump said in a video on social media. “They said, ‘What color would you like, sir? It’s called American flag blue. I said, ‘That’s the color I want; I want American flag blue.’”

Mr. Trump said the renovated pool would last “for 40 or 50 years.”

“There’ll be no leaks; there’ll be no anything,” he said. “It’ll look gorgeous, beautiful.”