Today’s technology requires pure water and much of the water “requirement” involves wastewater from the purification process. Saline or polluted water can be used, but it must be purified before going to the electrolyzer cell. The less pure the inlet water, typically the more water and energy it takes to make hydrogen due to the need to purify the water. There is work on electrolyzers that can take saline or brackish water, but these are not yet (2021) commercially available.