The Rainbird jartop valve that is connected to my dripper line creates a repeating thumping noise. Sometimes it only starts after you turn on a fixture in the house, sometimes it starts as soon as it turns on. This is different from a water hammer that happens once at opening or closing, this will keep going thump-thump-thump indefinitely until the valve is closed. I have installed a water-hammer arrestor next to the manifold, but the problem occurs with or without it. Thanks!
