About Gravity Feed Drip Systems

Drip irrigation products are designed for use with constant pressure of 15 - 30 psi. The stated output for drip emitters (drippers) is based on this pressure. For example, the 1/2 gph emitters in this kit will deliver one half- gallon of water per hour if the system is pressurized at 15 psi.

Since the pressure with a gravity system is often well below this range, and drops as the system operates, emitter flow rates will be substantially less than those specified for the individual emitter. Output will also vary between emitters on the same line of drip tubing as they are placed farther away from the water source.

Drip Emitter Output drops down the line

In a nutshell, a gravity-fed drip system will distribute water inconsistently throughout the system.

To determine the water pressure in a gravity feed drip system, measure the height of the water in the rain barrel or tank to the ground.

Rain Barrel at 2 foot elevation

If the rain barrel is on a hill above the plants to be watered, measure the height of the barrel above the planted area. You gain .433 psi for each foot of elevation. For example, if you fill a 2 foot garbage can (or rain barrel) with water, the pressure is less than 1 psi (.866 psi). As the water level drops in the barrel, so does the pressure. The output of the drippers will drop as the water level drops.

At very low pressure, it may take several hours to deliver the amount of water needed for your plants. For example, if a dripper emits 1/8 of a gallon of water per hour with a rain barrel 3 feet above the ground, you need to run your drip system for 4 hours in order to deliver 1/2 gallon of water to your plants.

We have don extensive testing with our drip kits in multiple configureations in order to provide you with the best recommendations.  Our goal is to help you build a gravity-feed drip system with the most consistent drip emitter output.

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