I prefer 5HP because my market area operators like to push the limits…
#6 spray tips at 1,300-1,400 psi = 3.5 to 3.8 GPM
Those numbers exceed the 3HP motor’s specs…
1,300psi x 3.5gpm = 4550 / 1460* = 3.11 HP required
1,400psi x 3.8gpm = 5320 / 1460* = 3.64 HP required
*Cat Pumps Handy Formula...