SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

My first suggestion for a 1st-timer is to read www.irrigationtutorials.com if you have not already.

Second, I can tell you that the author of the above referenced web site gives the advice of making sure you have at least as much pressure in psi as you expect to have in throw in feet. So if you want to design for rotors throwing 45 feet, you need to have 45psi AT THE ROTOR. Since you are starting with 50psi, you are going to be pushing it to only loose 5psi of pressure. It might still be possible, but if you are going to be pushing 14GPM, you might need larger than 1" PVC to keep pressure losses at a minimum.

Additionally, when you say 14GPM @ 50psi, is that a dynamic measurement (which usually requires special equipment to test) or a static pressure test and the "fill a bucket" test (which usually gives higher values than a true dynamic test).

Without knowing more, I would recomend that you design for a head to head distance of less than 45 feet so that you have a little wiggle room and reduce the risk of winding up with a system that doesn't completely work.

Also keep in mind that you are not tied to only 30 or 45 feet just because your lawn is 90 feet deep. You can also layout the rotors in what is known as a triangle pattern. So you could design for say 40' throws. To start, you place one rotor in each corner, then you place another rotor in the center of the yard 40' from the edge (the center one fills in where the two corner heads don't reach for head to head coverage).