Evaporative cooling pad circulation pumps are much like fans, except they move water instead of air. Like fans, every model of pump has it own characteristics. We know from working with fans that there is more to selecting a fan than making sure it has the right size motor. Sure, a fan with a larger motor will tend to move more air than one with a smaller motor, but this is not always the case. Even fans with the same size motor do not always move the same amount of air. A 48" fan with a 1 h.p. ...motor can move anywhere from 18,000 to 25,000 cfm. Last but not least, all 48" fans with a 1 h.p. motor do not hold up to pressure the same. While the output of some fans will drop just a few percent as the pressure increases from 0.05" to 0.10", the air moving capacity of others will decrease well over ten percent. Because there are significant differences in air moving capacity between 48" fans with 1 h.p. motor , it is important that in order to maximize bird cooling that producers select a fan not by motor size, but rather by how much air the fan will move under typical operating pressures.