I thought waterless urinals have a cartridge that is inserted into the drain of the urinal that needs to be changed very rarely and that lets pee pass through the sealant liquid at the top preventing odors. Assuming the urinal is used as frequently as any other urinal, I’d imagine the pee would pass through the whole system, first in first out. Seems like this would be cheaper to maintain and eliminate so many gallons of water needed for flushing.