When water hits Topmix Permeable concrete, it doesn't flow in all directions, slicking up the surface.
It flows in one direction — down. And it vanishes almost instantly.
Traditional concrete has to be permeable enough to let a minimum of 300 millimeters of water an hour through to the ground level. That allows it to safely handle a major storm event every 100 years.
Topmix Permeable, in contrast, lets through 36,000 millimeters of water an hour, or approximately 880 gallons every minute.