Drip Irrigation Index
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How to choose a drip irrigation pressure regulator

Match the regulator to the pressure required by the line, the flow through the zone and the available inlet pressure while water is moving.

Three numbers to find on the regulator data sheet

Outlet set point
Compare the regulated pressure with the operating range of your exact line.
Minimum and maximum flow
Check the smallest and largest zones you intend to run.
Required inlet pressure
Measure upstream pressure while the zone runs and compare it with the requirement.

Read the line and regulator specifications together

Look up the operating range for the exact line. A manufacturer’s reference pressure in a flow table describes the test condition for that rate. The maximum operating pressure is a separate limit.

For the regulator, look for outlet set point, minimum and maximum flow, and required inlet pressure. Compare those limits to the smallest and largest zone you will run. A regulator can reduce pressure when the inlet conditions are adequate. It cannot increase the pressure available from the water source.

Size for the zone that actually runs

With 2,000 ft of Toro EA5081222-750 open, the published 10 psi flow of 0.25 GPM per 100 ft gives about 5.0 GPM of nominal zone demand. Compare 5.0 GPM with the regulator’s rated flow range and check its required upstream pressure at that flow.

If the same head assembly will sometimes feed just a small bed, calculate that zone too. The small zone can fall below a regulator’s minimum flow even when the larger zone works.

Measure pressure while the rows are running

Use an appropriate gauge at the regulated outlet and at a representative tape inlet, including the highest or farthest bed where practical. Compare these readings with the maker’s requirements. A low reading after the filter may indicate filter loss or inadequate supply.

Check pressure and flow again after adding rows or changing the filter. Use the manufacturer’s run-length chart for slope and uniformity before extending a lateral.

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

Sources