A broken head wastes more water than a short zone, and on Lewisville clay it also carves a hole in Bermuda before the bill arrives. Sun yards here are mostly Bermuda. Shaded older lots, including parts of Old Town and the southwest side, still hold St. Augustine that can cover a sunk head until only a wet circle shows.
What usually failed
Mowers take the cap off heads that have risen. Edgers along College and Main shear the riser. Summer heat shrinks the black clay, a gap opens around the body, and the head leans until the stream hits the walk. The swing joint, the funny pipe, takes that bend until it kinks or splits. A new nozzle on a tilted body still leaves the yard.
The head is replaced and set so the mower clears it. The nozzle matches the station: a strip along a fence is not the nozzle for an open front lawn. If the funny pipe is cracked, it is replaced with the head. Leaving the old swing joint is how the new head blows off on the next cycle.
When the head is not the cause
Low pressure on every head in one zone is often the valve, or a leak in the lateral, not a bag of nozzles. The zone is run before heads are sold. If only the last head dribbles, the search is a crushed pipe under a new fence or a root on an older pecan lot.
Call (940) 239-0007 and say how many heads you can see failing. One corner head is a short stop. A zone of sunk heads across a Hebron or Vista Ridge lawn is a longer one.