How Do Irrigation Water Pressure Regulators Work

Tuesday, April 15, 2014

The primary function of an irrigation water pressure regulator is to maintain a sprinkler system’s desired performance.

A well-designed irrigation system takes a predetermined amount of water and applies it uniformly over a specific area. The pressure regulator's role in this system is to maintain the desired performance by limiting excessive inlet water pressure to constant outlet pressure.

Proper use of pressure regulators helps maintain the overall efficiency of an irrigation system. Pressure regulators assure good sprinkler performance and can help lower energy costs and save water.

Manufacturers offer several models of pressure regulators to meet various irrigation needs: flow ranges, operating pressure rating, maximum inlet pressure, inlet and outlet connection size, and connection type - NPT, BSPT, and hose connection threads.

Pressure regulators limit excessive water pressure by automatically adjusting their opening area based on the inlet pressure. The opening changes proportionately to help assure the outlet pressure stays within acceptable limits.


The flow of water running through the regulator's inlet end and around the fixed seat causes the pressure regulator to come on.
The flow of water running through the regulator's inlet end and around the fixed seat causes the pressure regulator to activate.


A pressure regulator activates when water travels through the inlet end of the regulator and around the fixed seat, as shown above in the dark blue area. The flow of water enters a hollow cylinder called a throttling stem (or t-stem), which is attached to a larger diaphragm near the outlet end. There is a spring around the throttling stem that holds the flow area open and lets water through.

When water passes through at high pressures, the excess pressure acts on the diaphragm and forces the spring to compress, pushing the t-stem toward the seat. The opening near the seat closes just enough to maintain the desired pressure and flow. The balance between the force on the diaphragm and spring resistance establishes the outlet pressure.

What is a performance curve?

Every pressure regulator is designed to operate at a minimum and maximum inlet pressure and a predetermined flow range. A regulator performance curve illustrates how the pressure regulator will perform within the model's range of inlet pressures and flows. The Y-axis shows outlet pressure, and the X-axis shows inlet pressure.


Performance curve.
Rogers, Shaw, Pragada, & Alam, 2010.


In the chart above, the blue band for the 30 psi (2.07 bar) model shows the performance at various flows. At the lowest flow (0.5 gpm or 113 L/hr), the regulator will maintain an actual outlet pressure slightly higher than 30 psi (2.07 bar). At the highest flow (15 gpm or 3407 L/hr), the actual outlet pressure is slightly lower than 30 psi (2.07 bar).

Check out the performance data of all PSR-2 models featuring a design that makes them ideal for use with surface water.

What do water pressure regulators mean for your sprinklers?

Sprinklers are made to operate within a specific range of flows and pressures. This keeps their application pattern uniform and produces the correct droplet size.

Basically, sprinklers can only pass along what they receive. Give them consistency and they’ll return the favor. Most sprinklers perform best at a specific pressure range, often lower than your in-line pressure. Pressure regulators assure operating pressures do not exceed a manufacturer's recommended operating pressure range. They also help prevent fittings and emitters from blowing out of the tubing because of pressure surges.

But note that in-line pressure should be at least 5 psi (0.34 bar) higher than your regulator’s designed outlet pressure!

Going in-depth into pressure regulator fundamentals

Check out the pressure regulator guide to learn more about the importance of maintaining correct system pressure to conserve water and energy, troubleshooting tips, and answers to FAQs.

Learn the fundamentals of pressure regulation with Senninger's free on-demand pressure regulation course on Hunter University. Learn how to install pressure regulators in different irrigation systems, select a model, identify wear issues, causes of pressure fluctuations and more.

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