Are you talking about something to hook to a hose, or are you going to do it right and put in a sprinkler system? Most sprinkler controllers have a circuit to start a pump. You don't need a pressure tank. The pump starts momemtarily before the zone valve opens and shuts off when the cycle is done. Depending on where you are and how comfortable you are with tackling a project like this, your local irrigation supply house would be a great place to start. John Deere Landscapes carries all the major brands and sells to both contractors and Joe Homeowner. Ewing Irrigation has offices throughout the Southwest and Midwest. Either one will sell you the pump, a proper screen and filter set up and help you layout your sprinkler system and choose the right equipment for what the pros call a "dirty" system. It is not as expensive as you might think. I just did an acre of lawn for around $2,000 including trencher rental.