What can cause sprinklers in the same zone to have a lot less pressure than others (besides clogged heads)?

Question

I have two sprinkler heads that have really high water pressure and another area on the same line has very low pressure. There is a history of pipe breakage but I think I blew all of the mud out. I have checked all of the head filters and they are clean. Could there be a rock in the pipe? If so, how can I isolate it?

Answer 1

First of all, unscrew the top of the head from the body and check inside. If the filter is removable, then remove it to make sure there is absolutely nothing inside. It is also possible there is something blocking the nozzle. Small items sometimes pass the filter and get lodged in the nozzle. Put a pin in the hole in the nozzle to clear anything out. Typically the reducer fitting before the funny pipe (3/8" pipe) gets clogged. Dig up the 3rd head and remove it. You need to be able to remove the reducing fitting. Hopefully it is a male adapter so you can just unscrew it instead of cutting it, and look for rocks (the head could be screwed directly to the pipe, if so just remove the nipple). If you see rocks, fish some out with a pair of pliers or marker flag or something similar. (If there are enough rocks in the fitting, and you just turn the water on. nothing will come out.) When some are fished out, turn the water on to remove the rest. If this doesn't work, cut the fittings out and blow out the lines. If there are no rocks, you could have another fitting before that, that is holding a rock. Let's hope that is not it. That would be a problem. If it was a slow loss of pressure, say over a season, it could be tree roots. If none of this helps, you can either replace the line from the second head to the third head, or put a smaller nozzle in all heads and turn the run time up on that zone in the controller.

Answer 2

You are correct, you have a plugged line. You need to dig up the last head in the line, remove the barb fitting from the line, turn on the water to the zone and let it blow.

Answer 3

Firstly, you may have a leak. Check the line after the two that work, and clamp the outgoing, test them, include one more, clamp off the further ones and test.