Yes I did look at some of those web sites for the calculations.
However the problem is I have two runs that serves different parts of
the yard and I have yet to discover all the heads and there are areas
that the two runs partially overlap and I do not know which head is
from which run. I fixed a few heads last weekend and once they are
fixed I then realized I have another stretch somewhere else that when
along the perimeter of the property line then under the driveway and
back up on the other side of the sidewalk.

So what I am trying to say is it's impossible for me to know all the
heads and all the run and branches at this time without me digging
them all up, so I am trying to use the best judgment I can to fix a
partial section of it by knowing that the existing configuration works
so trying to isolate the subsystem and establish it's boundary
conditions. The water supply is from a well pump.

MC