Noise in house pipes when sprinklers run
House is on city water in San Jose, CA. All plumbing inside (1/2") and outside (3/4") is new copper pipe except sprinkler pipes (3/4" PVC). Each sprinkler station has anti-siphon valves.
There is a continuous loud noise like water is rushing or gurgling in all pipes inside house for the duration when sprinklers run. Noise comes only if main valve for sprinkler line is half open. If sprinkler's main valve is completely open then there is no noise while sprinklers run. I do not want to open it completely as sprinklers throw water too high and more water is wasted. I will try adjusting sprinkler heads to see if that helps but am wondering if there is something basic wrong with plumbing.
Thanks