Drip/Low volume irrigation systems operate at much lower pressures than sprinkler systems, and so a pressure regulator is usually required to bring the dynamic pressure down to an acceptable range, normally between 15 and 35 psi. A drip system that operates at high pressure (above 40 psi) may appear to be operating adequately; however, it is more likely to develop problems over time.
The most common pressure regulators designed for drip irrigation systems are non-direct acting pressure regulators that have a pre-set output— they are not adjustable. These regulators are not suitable for continuous pressure applications; that is, they must be installed downstream of the system control valve where they will only be under pressure when the system is running. These devices are frequently connected to the Y filter outlet and installed in the same valve box adjacent to the system control valve. These regulators must have a minimum amount of water flowing through them or they will not lower the pressure at all. Therefore, in order to select the appropriate regulator, it is essential to know the total flow rate of the system on which it is to be installed.
Although most of these plastic, pre-set regulators look similar, all pressure regulators are not created equally. The quality and durability of these regulators varies greatly between manufacturers. Consider only commercial-grade models made by a reputable global manufacturer. And check the specs and look for features like a minimum 2-year warranty, and models that have a maximum inlet pressure of at least 120 psi or more.
Direct-acting pressure regulators are another type of pressure regulator which are suitable for mainline installations, where the device will be under continuous pressure. These regulators are usually brass, adjustable, and available in different ranges and sizes. When mainline static pressures are high, direct-acting regulators are sometimes necessary to install on a mainline upstream of the control valves, to bring the static water pressure down to an acceptable level.
EDiTor’s NoTE: Stuart Spaulding, CLIA, technical service manager for DIG Corporation.