At the point that it leaves the body, urine is mostly sterile. In a normal toilet, it is actually the mixing of urine and water, not the urine alone, that encourages bacteria to grow and spread [source: Reichardt]. Once the particulates and minerals in urine react with the minerals and chemicals in water, bacteria begin to thrive. Since there is no water introduced in a waterless urinal, there is less bacteria growth. The sealant in a urinal also keeps it from being exposed to air, where bacteria travels and spreads. Flushing urinals can also send small water droplets into the air, which can spread bacteria throughout the bathroom and even onto your hands or clothes [source: Waterless]. Waterless urinals don't create that problem.
Still, like any bathroom fixture, you need to clean waterless urinals regularly to make sure they stay clean and bacteria doesn't find a place to latch on and grow. Cleaning them is relatively simple: You can use a household cleaning solution and a sponge or cloth to wipe down the exterior surfaces [source: Zero Flush].