The president pushes for more flow from the nation’s shower heads.

President Trump has complained before about the sorry state of the national water pressure. Now he is transforming grievance to governance, trying to roll back a regulation limiting flow through American-made shower heads.

Mr. Trump often eschews written briefing materials and ignores even basic policy matters, according to former administration officials. But he has often focused on minutiae pertaining to matters of personal importance, peeves emanating from his days as a developer and landlord. Low water pressure, often an issue in Manhattan high-rises, is one of them.

“So shower heads — you take a shower, the water doesn’t come out,” Mr. Trump said at a an event touting his business-friendly policies in July. “You want to wash your hands, the water doesn’t come out. So what do you do? You just stand there longer or you take a shower longer? Because my hair — I don’t know about you, but it has to be perfect. Perfect.”

A federal law enacted in 1992 mandates that new shower heads not be allowed to spritz more than 2.5 gallons of water per minute. The Obama administration, target of so many Trump-era anti-regulatory assaults, dictated that the 2.5-gallon cap be applied to the aggregated outpouring of all nozzles in modern-day multihead shower fixtures.

Mr. Trump’s Energy Department proposed a new rule on Wednesday that would allow each nozzle to pump out 2.5 gallons, with no restrictions on the total.

Environmental advocates say the plan is no trivial matter: It could lead to waste of water at a time when large sections of the country are grappling with multiyear droughts.