Hello again, Yes, actually both Ricks here operate Gandis... I have got to believe it is related to changing out those 4 heads. I would suggest disconnecting and capping each of the new heads, one at a time. After you prove it is not related to the new head installs, go back to the pump lines and start the same process. Keep capping lines and watch the pressure dial until you find the leak If you cap a line and the pressure holds than you know the leak is between that point and the heads... keep narrowing it down. Not much fun