Most sprinkler systems I've seen or dealt with have T's installed in
the lateral PVC lines with the opening pointing up and the sprinkler
heads screwed into that.
I just dug up part of my sprinkler system as I want to move a few
sprinklers to add a patio. The way the builder put in the sprinklers
(pop-ups) was with the a threaded T opening to the side, an L-shaped
adapter screwed in with about a foot of black flex tubing running
(parallel to the white PVC pipe) to a vertically oriented L joint and
the sprinkler head screwed into that.
Is this a very good installation method? A very bad one? Or just a
strange way of doing it? One plus is that it would seem to allow for a
lot more flexibility in placing individual sprinklers. It would also
seem to cost more for a new install and this builder was not known for
spending on quality, to be diplomatic, hence my consternation..