I'm not a pump expert by any means, but I believe you must determine how many gpm of water you need to operate the sprinklers then get a pump that will supply that much, probably with a little extra just to be sure. Sprinkler head wear and get a larger diameter thereby putting out more gpm than originally rated, you may add to the zones, and it's nice to have a reserve so you're not always maxed out. Something like have a little more HP in you car than you really need. Some of the pump experts might have some additional thoughts.