A pressure regulator's basic function is to maintain an irrigation system’s desired performance.
An irrigation systems is designed to take a predetermined amount of water and apply 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 a constant outlet pressure.
Pressure regulators accomplish this 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.
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. 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 does this 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
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.