The reversal is largely meaningless; the majority of showerheads on the market today comply with the 2013 rule that Mr Trump sought to undermine with his policy. Some showerheads that allow expanded flow do exist, but they are relatively rare.
Mr Biden's ruling will bring the nation officially back in line with the 2013 rule.
Showerheads have had flow regulation in the US since 1992, when it was determined that new showerheads would not allow more than 2.5 gallons (9.5l) of water per minute.
As showerheads evolved and began to feature multiple nozzles, some manufacturers skirted the limitation by designing each individual nozzle to provide 2.5 gallons of water per minute. In 2013, an Obama-era rule tightened the regulation. It specified that the combined output of all nozzles on a showerhead can equal no more than 2.5 gallons of water per minute.
Mr Trump had a problem with that, so he reversed it in December.
“So showerheads – you take a shower, the water doesn’t come out. You want to wash your hands, the water doesn’t come out,'' Mr Trump said at the White House in 2020. “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.”
The 2020 rule also created language for a "body spray”, which is essentially a showerhead that sprays water horizontally rather than from a vertical position. The inclusion of "body spray" was essentially another method of trying to skirt around the water conservation rules.
Officials in the Department of Energy estimated that the Obama-era rule saved households approximately $38 a year.
The Department of Energy “believes the 2013 definition of a showerhead strikes the right balance by allowing consumers to continue to have showerhead choices in the market, while placing an emphasis on water conservation and reduced utility bills”.
Mr Trump's shower crusade did not appear to resonate with many people, even his hordes of unquestioning fans. According to Consumer Reports, there is no indication of mass dissatisfaction with the state of showerheads in the US. In fact, most showerheads in the US – 74 per cent – use two gallons (7.5l) or less per minute, which is even lower than the federal standard.