I have two sprinkler heads in the same zone that suddenly have low pressure. The zone has six identical gear driven sprinkler heads. They all worked well (equal pressure) until just recently. Then two heads on the farthermost end of zone began putting out less water, perhaps a fifth of the other heads.
First, someone said the heads were clogged... so I just replaced them with new heads (they were 5 years old). However I got same low output with the new heads.
Then someone said I had an underground leak, so I removed all six heads on the zone and capped them. I put on a pressure gauge on each head in the zone. The pressures were identical. The pressure goes up to 90psi and holds until the zone shuts off then falls back to zero psi.
Maybe they should hold the pressure after shutoff but not sure if there is a pressure relief valve somewhere. Anyway...
I see no indications of a leak in the lawn surface, no pooling water, etc...
The only thing I can figure is that somehow the 1/2inch pvc to these two heads has become pinched (perhaps by tree roots).
Anyone have any ideas how to go about finding the problem except digging up the lines that feed the low pressured heads? I am afraid that even if I dig up the lines I will not be able to see the pinched line. It may un-pinch when I remove sod or roots from around the pipe and I will not even notice they problem area.
Secondly, maybe there is a clog midway in the line that, when capped, the line will still build up to the same pressure, but with head installed the clog restricts water flow? Can not understand how a clog would not blow itself out to the head.