Drip Irrigation Index
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How to choose drip tape emitter spacing

Choose spacing based on how the crop is planted and how water moves through the bed. Check the rate per 100 ft before committing to a closer spacing.

Same Netafim emitter, two spacings at 10 psi

8 in. spacing
About 150 emitters per 100 ft. At 0.16 GPH per emitter, the line needs 0.40 GPM per 100 ft.
12 in. spacing
About 100 emitters per 100 ft. At the same emitter rate, the line needs 0.267 GPM per 100 ft.

Check whether adjacent outlets wet the same strip

In coarse soil, water tends to move downward faster and may spread less to the side. Closer emitters can help a dense row where individual wetted spots would otherwise leave dry gaps. For widely spaced plants, place outlets where the roots can use the water and check the wetting pattern after a normal run.

Test two or three outlet intervals on a short length of the actual line. Dig across the row at root depth after watering. Check the space between emitters as well as the distance from the line to the crop. Surface dampness alone can miss a dry root zone.

Compare spacing and line flow separately

The Netafim example holds the emitter flow at 0.16 GPH. Manufacturers can also pair a different emitter rate with each spacing. Rivulis lists 0.34 GPM per 100 ft at 8 psi for both 508-08-340 and 508-12-340. Compare the listed line-flow rates for the exact parts you are considering.

Recheck the zone after changing spacing

Multiply the new line flow by the total active length divided by 100. Then check the available flow under pressure and the longest lateral. If the new zone exceeds the water supply’s capacity, consider dividing the rows into separately operated zones.

Look up the specifications for your drip tape or calculate flow for your rows.

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