The Trump administration has relaxed a regulation restricting water flow from showerheads, a pet peeve of President Donald Trump, who complained that he wanted more water to make his hair “perfect.” Since 1992, federal law has dictated that showerheads shouldn’t spew more than 2.5 gallons (9.5 liters) of water a minute. As newer shower fixtures came out with multiple nozzles, the Obama administration updated the ruling, stating that 2.5 gallons was still the limit regardless of how many nozzles were running. The new ruling, issued on Tuesday, now says each showerhead can emit 2.5 gallons a minute. “So showerheads —...