For your pump settings, you have too much pressure. The pressure in the tank (with the pump off and all water pressure removed - i.e., let the water flow until it stops on its own), you should have 1-2 pounds LESS than the low pressure turn-on point (18-19 pounds for a 20-pound low pressure setting). WIth that much pressure in the tank, the pump would see more pressure than its high point, and may not turn on and fill the tank. But, since there is no water in the tank, as soon as you open a sprinkler, the pump would turn on, since there is no water under pressure compressing your bladder, the pressure would drop to zero immediately. That is very low pressure, so your performance on the sprinklers may not be great. You may want to bump up the pressure, if the pump and water supply can handle it. Think of your pressure tank as just a storage tank pressurized by the pump. It gives you some water under pressure so that the pump doesn't need to run continuously as you turn water on and off - it won't raise your water pressure.