I have a Hunter Pro-c controller with hunter pop up sprinkler heads on 2 zones. I have a 3rd zone that has drip lines run off of it. the house has a main control valve and the sprinkler system has a main control valve. The 2 popup sprinkler zones work fine. However, the zone that has the drip lines has a terriblesqueal/whine in the house pipes down by the main valve. If I adjust the pressure in the main valve on the sprinkler system side, the squeal goes away. However, it has returned. I readjus...
