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Gravity feed drip irrigation systems

About Gravity Feed Using Drip Irrigation System

In gravity feed irrigation systems water takes the path of least resistance. If you place drip tubing or garden hose on the ground and punch holes every few inches, the openings closest to the water source will discharge much more water than the openings farther down the line. If the distance is long enough, water may not reach the last holes on the line. Distance could be as long as 50 feet or as little as 10 feet. This will depend on the height of the bucket/barrel, the pressure available, the size of the pipe and the flow uniformity of the system.

By selecting a low flow dripper, such as .5 GPH (2 L/H), and then raising the pressure by raising the height of the bucket from the ground, the efficiency and uniformity of a gravity feed drip irrigation system can be improved the use of drippers gives better control of flow rate than poking holes in the tubing, and the water passage structure of the dripper gives a better uniformity to the irrigation system.

With gravity feed drip irrigation system you may need to fill the barrel daily, or every other day. The only ways to adjust the time to empty the barrel, or to adjust the drippers' flow rate, are to close the ball valve in front of the barrel, change the height of the barrel, the volume of the barrel, and/or the total number of drippers in the system. Note that with gravity feed systems the size of the system is limited by the size of the barrel; in general, a barrel large enough to provide adequate flow and pressure to increasingly larger areas would quickly become unmanageable. As more outlets (drippers) are added to the line, uniformity decreases, with more water at the beginning of the line and less at the end. In addition, as the water level in the barrel drops, the drippers' flow rate drops.

To have an effective gravity feed drip irrigation system; consider the size of the barrel and the number of drippers. Our suggestion is to make sure that the flow rate per outlet is at least .03 GPH

Like drip irrigation system, gravity feed systems using drip irrigation need a minimum pressure to operate. To gain pressure in gravity feed systems, use this calculation:

To gain water pressure by using gravity means you must raise the water source (barrel) above the system lines. For every 1' (12 cm) of elevation above the system there is a gain of .433 PSI (.030 bar). This means that if the water source is 10 feet (3m) above the system there is a pressure of 4.33 PSI (.30 bar) at the start of the system (.433 x 10 = 4.33).

Keep in mind that low pressure, such as 4.33 PSI (.30 bar) or less, will lead to:

  1. Limited distance to the layout the 1/2" or 1/4" drip tubing.
  2. Reduction in the flow rate (.5 GPH recommended) for the drip emitters to considerably below the manufacturer's suggested flow rate.
  3. A drastic drop in uniformity once a certain length is exceeded.

Installing gravity feed drip irrigation system using a 50-gallon bucket

10 x 12 foot gravity feed system with 5 rows, each 10' long using a 1/4"drip line with pre inserted drippers every 12" (30 cm):

The chart below is for a gravity feed drip irrrigation system using a 1/4" drip line with drippers every 12" (30 cm). This design uses a 10 gallon (38L) bucket with 9 gallons (30L) of water at a pressure range less then 1 PSI on flat terrain

Barrel Size Height above the drip system Length of drip line run Dripper Flow rate Container close to empty in:
50 gallon 8" 10' .034 GPH 1.28 l/h Around 2.50 hours
50 gallon 12" 10' .036 GPH 1.36 l/h Around 2.40 hours
50 gallon 12" 14' .041 GPH 1.55 l/h Around 2.30 hours
50 gallon 16" 14' .042 GPH 1.58 l/h Around 2.20 hours

Installation of gravity feed drip irrigation system

  • Drill a 3/4" hole in the barrel about 1" from the bottom (if no outlet).
  • From inside the bucket insert a 3/4" x 1" nipple with o-ring model SWF013.
  • From the outside of the bucket, thread a model A029 3/4" adapter to the nipple.
  • To the adapter connect a 3/4" filter model F303.
  • To the filter connect a ball valve model A123.
  • To the ball valve connect a 4" to 10" section of the 1/2" drip tubing.
  • To the drip tubing connect a 1/2" elbow model LF007.
  • From the elbow to the ground add another section of 1/2" drip tubing model T004.
  • To the end of the 1/2" drip tubing add an additional elbow model LF007.
  • From the elbow lay out the drip tubing model T004 to the garden and connect to the elbow.
  • Near each row of plants punch a hole in the 1/2" drip tubing and insert a 1/4" barb model SF001.
  • To the barb connect 10' of 1/4" drip line with drippers every 12" model T047.
  • To punch the hole in the 1/2" drip tubing use punch model A019.
  • Fill the barrel with water and turn the ball valve on to flush the line, and as the water is running, close the end of the 1/2" drip tubing using hose end model A006.
  • Close the end of the 1/4" drip line using the small side of the goof plug, model SF007.