Chris Lewis wrote:

According to Ray K :


Two of the five heads pop about 1/4 inch, instead of the full 4 inches,
and dribble a small amount of water. They happen to be the lowest ones,
but the lawn's slope is really pretty gentle, maybe five degrees.





In the room containing the water meter and the main shutoff valve, I can
hear the water running to the bad zone. I timed how long it takes for
the water meter to move a certain amount. The 14 seconds the bad zone
takes is in line with the 14-19 seconds the other four zones take. This
rules out a partially opened zone valve and a blockage in the pipe run
between the zone valve and the head nearest it. It does suggest a break
in that run. What's puzzling is that the water would be absorbed in the
heavy soil surrounding the break at the same rate that water would leave
the five heads if there were no breaks.



You'd be surprised at how much water can disappear. It's coming out
under pressure, and if the jet is _downwards_, it may be building its
very own sink hole. If the jet was _upwards_, you'd probably have
a geyser.

Before starting to rip anything up, try removing the heads themselves. The
strainers may be plugged with grit. Them being the lowest ones is
suggestive.

Are the slow heads adjacent to the valve, or the t'other end?


No, they are at the most distant end.

Thanks,

Ray