Could be. Remove the head and turn on that zone -- see if you have good flow at the head in question. Also look for broken/leaking fittings on the pipe, or even the pipe itself. Any wet areas creep up? I had a smiliar incident... ended up being some gravel in the line at the head

u, Sounds good to me but then again I don't have to winterize. There are many past threads on this subject with the compressor size to use. I don't think any damage will result if some water is left behind as long as there is room for the water to expand as it freezes. Aloha

greg, JMHO, you don't think you have much to worry about. You could do the winterizing the system yourself. Check out the YouTube vids on the subject. aloha

Ours system has been in for 23 years. It was self installed and was built with a drain plug at the lowest level that could be manually opened to drain the main. The plug was installed with a valve cover over it to get to it easily. We would turn off the valves at the BFP, stuff a towel around it in the box, and drain the system every year in the late 80's and early 90's when we were expecting really cold weather for several days. In the past 6 or so years we haven't done anything to winterize it since the winters haven't brought any sustained cold weather, and we do run it periodically in the winter if we haven't had much precip and a cold snap was coming. I don't think the shrub heads keep water in the pipes - they seem to drain back into the underground pipes, (after 23 years we probably have some tiny leaks) so as long as they are empty, they shouldn't get damage.