I am planning a new tree nursery, and am exploring the gravity-fed water system options. There is room to place 2,146 trees in the area, they each require 2.5 gallons of water every day. I want to use 1 gallon per hour (gph) drip emitters and break the trees into 17 different zones with a maximum of 128 trees per zone. The drip irrigation requires 20 psi to work properly, and a reducer can be installed to keep the pressure from being too high. Assuming these are all on a level surface, what size tank would I need with what dimensions to keep the lines pressurized with a minimum of 20 psi after a daily 5,365 gallons have been applied?
1 Answer
I don't think the size of your container will affect the pressure of the water contained in it, as much as the depth of the water. If you want to have $20 \; psi$ and the entire system is on level ground, then you will need to have a container with the water level at a minimum of roughly $46 ft$ tall. $Pressure (psi) = \frac{Volume}{\pi R^2}$ where $R$ is the radius of your cylindrical container. That gets you the height. To convert that height to $psi$, just multiply the value by $4.333$. That's how I got the number $46$. So, in conclusion, you want to have your water source at $46 \; ft$ above where you want there to be $20 \; psi$ (Note that you don't need to have $46 \; ft$ of water, rather the water is just $46 \; ft$ above the system).
If you think about it, the rather large number makes sense because that is how water towers function. I hope this helps.