Question
Hi Jim,
I'm in Maputo, Mozambique, trying to figure out, with your help, a gravity
drip irrigation system for my 2 hectares (20.000sqm) land. I have already a
200 cubic meter water tank 1,5 meter above the ground. And a diesel water
pump that supply 36.000Liters/hour from the nearby river. My intention is to
divide the land into 20 plots, each with is 1.000sqm to grow mainly
vegetables. All plots will be interconnect but fitted with valves to water only
the plots or plots needed at specific times. I intend to use low flow drippers.
My specific questions are:
1. Will the gravity system be suitable for this endeavor?
2. The water pipe that comes out the main water deposit should be of what
diameter? And the pipe diameter of the main lines?
3. Pressure regulators could be applied in gravity systems?
Your help will be very much appreciated.
Best regards
Salvador Emidio

Answer
Hey Salvador, I hope this helps. #1 As long as you can get about 30psi(pounds per square inch) pressure you should be fine. You could always raise your tank up higher to increase your pressure. #2 I would stay with at least a 1 inch line to run from the tank and have the valves feed off of this 1 inch line. As far as the lateral lines (lines you would hook the drip emmitters into) it will depend on how far the lines will run, and how many emmitters you intend to put on each line. 1/2 inch or 5/8 inch poly pipe you could run about 300 to 360 gph(gallons per hour) or about 300 to 360 1gph emmitters. With this line, you probably don't want to run more than 400 feet. 3/4 inch pipe you could run about 700 gph or about 700 1gph emmitters. With 3/4 inch line, you probably don't want to run more than 750 feet. With 1 inch pipe, you could run about 1100 gph or about 1100 1 gph emmitters. With 1 inch line, you probably don't want to run more than 1000 feet. #3 You would install a pressure regulator after each of the valves. Normally you want to be at about 30 to 40 psi( pounds per square inch). If the pressure coming off your tank is less than 50psi, I would not worry about putting on regulators. Let me know if I can help you anymore, thanks and have a great day.