It ramps the water in, not like "on or off" it STARTs at 5psi then ramps the pump voltage up as boost rises until gets to 13.5V at full spray. Its adjustable from when it comes on to when it hits full spray.

If you have a "on/off" type, and try to spray at 5psi, you might get too much water for only 5psi ( kick pisses the car off sometimes ), and then on the other end, at 20psi the nozzle might not be big enough b/c if you use a bigger nozzle the water "quinches" the combustion at 5psi.

Another words, this lets you run a big nozzle, and still not add too much water too soon.

Not to meantion it comes with the bad ass connections that just snap together with no leaks.