Use of low-flush toilets started in the 1990s after President George H W Bush signed the Energy Policy Act. The 1992 law said new toilets could use no more than 1.6 gallons of water per flush. The law went into effect in 1994 for residential buildings and 1997 for commercial structures.

“You go into a new building, a new house or a new home and they have standards and you don’t get water,” Trump said. “You can’t wash your hands practically, there’s so little water that comes out of the faucet. And the end result is you leave the faucet on and it takes you so much longer to wash your hands and you end up using the same amount of water.”

Trump said relaxing water-conservation standards might not be practical in some arid regions of the nation, but he claimed in many states, there is plenty of water. ‘‘It comes down. It’s called rain,” he said.