All trees and small fruit in the WWFRF fruit garden are watered from a drip irrigation system. The drip irrigation tubing consists of in-line emitters spaced at 12 inch intervals. All drip lines are buried 4 to 6 inches deep and are fed from a 2 inch PVC pipe surrounding the garden perimeter. The entire system is turned on by one hand-operated shut-off valve. We water the garden once per week for four hours during the summer months.
The following diagram lists the critical parts and layout of a typical system.
Overview — Drip irrigation systems begin with a faucet assembly consisting of a back-flow prevention device and a filter, plus connectors leading to the main water supply pipe which runs underground to the manifolds in valve boxes (available at plumbing stores). Each manifold will have multiple valve/pressure regulator units, each leading to a different zone. A system is divided into zones because, unless the system is very small, the water supply will only be able produce enough gallons per hour to water part of the system at a time.
Water supply — To determine the GPH delivered at the faucet fill a large bucket for 30 seconds at maximum flow. Then measure the amount of water and multiply by 120.
Drip line — Chose an appropriate drip line for your soil type. For instance, for loam soil 0.6 GPH with the drippers at 18 inches. If the system could supply only 180 GPH, then at 41 GPH, up to 440 feet of drip line could be used for each zone, but some allowance should be made in case other water usage lowers the pressure.
Pressure — Use 25 or 35 PSI pressure regulators, with the higher pressure being for larger zones.
Zones — Try to arrange the zones so that they have plants with similar water requirements, since some plants need more water, more frequently, than others.
Use the charts below to find the correct drip line and calculate length of drip line for each zone. Be sure not to allow the single lines to exceed the maximum length for the pressure.