Will This Sprinkler System Work?

Question

I have put in a new water sprinkler system in my yard. The total yards of the system is approximately 100 and I ran 3/4 inch thin walled pvc pipe for the trunk line and 1/2 inch pvc thin walled for the feeder. I have 39 nozzles which discharge 2.3 gallons per minute or 89 gallons total. My line connects to the main water supply line at both ends. My question are 1) how much volume and pressure do I need to make the water system opperate properly and 2) can I do it with what I have installed or 3) do I need to add a holding tank and pump? Thanks

Answer 1

You need more pressure than will be practical to make this undersized system work properly. Without a layout I can only give an approximation.
For the flows shown you will need a minimum 11/4 " for headers at 45 GPM each with a pressure loss of about 10 PSI per 100 ft..If 1/1/2" pipe is not that much more expensive use it. However, consider the comparative costs to the two valves and the fittings.The nozzles will each have 1/2'' connection feeders which pipe you can reuse. .The branch lines off of the headers will be sized for the number of nozzles each. A 1" branch will accommodate about 4-5 nozzles at about 8 PSI /100 ft. Or reuse your 3/4" pipe for 2-3 nozzles each run.The nozzles themselves might need 15-20 pisg at their entrance. Three hundred total ft of straight pipe at 8-10 psi per 100 will be about 30 psi plus 15-20 for the nozzles. Add some extra loss for fittings. About 55 pisg will probably work.
The pressure and flow available from the source will determine the need for a storage tank and a pump. If you overload the existing system. you will lose pressure in the rest ot the overall system served by the main supply.
If the main supply has a pressure regulator, your flow will be limited to the flowing capacity of that valve.
For the first operation run it without the nozzles to flush debris out. If you can put a cone-shaped screen in front of each nozzle, they will stay unplugged longer.