Hi js, WOW! This is one of those puzzles that has more unknowns than equations. How many irrigation zones? What is the flow rates and time for the sprinklers to max out? What is the capacity or size of the 3 tanks? How are the tanks hooked into the system? How much peak flow do you need for your house, if everyone flushed, brushed there teeth, did the laundry and washed the dishes at once? When does your geothermal pumps need to be running? Is the lawn split up into sections like front, back, side to side? What type of plants do you have in the beds? 1" of water for 100 sf of lawn per week is 63 gallons. Times 150 for your 15,000 sf is 9,450 gallons each week plus or minus for seasonal changes. Water your lawn and vegetables at night when you are asleep. Do a 24 hour matrix scheduling the quantities for all your uses and storage. Your pump designer/installer should be able to make sense of it all. Good luck. Aloha

How can one accurately quote without a static pressure reading?? If , based on his numbers all the heads are quarter circle, then 10 heads x .81 gpm = 8.1 gpm flow. That alone is just outside the industry standards for flow in a 3/4" sch. 40 pipe. How likely is it that they would all be quarter circle?? If they are all half circle then 10 heads x 1.52 gpm = 15.2 gpm flow which is way out of line. Pressure loss per 100 ft. is around 18psi at that flow. Knowing the static pressure is important for that reason alone. Forget it if you add any full circles to the mix. There are other variables that affect how much water can be run but we do not have that info because we can't see the site. Based on what info you have given, I do not see this zone as operating very well. We generally do not run more than 8 gpm on a 3/4 pvc line and the conditions have to be right. High flow rates in a small diameter pipe bring along other problems such as water hammer noise.

Thank you for the replies. 1) Starting pressure: Since the well is not dug yet, it's going to be prejections. But assuming I will get a free-flowing well like my neighbors (contrators say the same), I am going to have an aboveground spinkler pump, 1 1/2hp. Immersible turbine pumps can get esaily damaged by lightning in my area, according to my neighbor. It is limited by 45 psi shut-off pressure. So, 40 psi discharge pressure is reasonable. 2) I am not using a jet pump. According to the expert at the store I called, irrigation needs irrigation pump, not jet pump. Jet Pump can give pressure but cannot keep up with flow rate. 3) I am not usign a pressure switch or a tank. Again, according to the expert, irrigation needs a well and a pump. Don't use anything else, according to him. 4) Someone mentioned delta pressure of 2 psi at the sprinkler head. That is much assuring. 5) I am oversizing everything to minimize pressure drop. 2" lateral is an example. I really don't need this size. 6) Still, the valve pressure drop bothers me. I can see that there needs to be certain pressure drop across valve for proper operation (more for opening than closing?) But 4 or 5 psi? I am not convinced. I am going to use 1 1/2' valve. 7) In the worst case, I will go with microirrigation. (I am not watering lawn. I am watering plants, some in pots some in ground). That will cut down everything, pressure need and volume need. But I have to run black poly and 1/8 feed lines and micro irrigation heads. Thank you for sharing your experiences. I would not have know about water stream blown by wind at 40 psi, for example.

40-50psi may not be sufficient either. The company that installed my sprinklers used around 65psi to winterize my setup this morning. This was higher than I expected so I asked him about it and he said anything under 45psi gives iffy results unless you're willing to spend a lot of time doing it. Even at 65psi with a tow-behind compressor, it took a good 20 minutes to blow out 4 zones. I'd imagine it would take the better part of an afternoon to do so with my little 15 gallon compressor.