What are the two main types of pressure regulators used in irrigation?

The correct choice identifies the two main types of pressure regulators commonly used in irrigation systems: adjustable and fixed pressure regulators.

Adjustable pressure regulators are designed to allow the user to set and change the output pressure according to the specific needs of the irrigation system or the particular plants being watered. This flexibility makes them useful in varying conditions where different pressures may be required over time or depending on different zones within an irrigation system.

Fixed pressure regulators, on the other hand, are manufactured to deliver a specific output pressure that cannot be altered. They provide a consistent level of pressure, which can be beneficial in setups where uniformity is crucial, ensuring that all areas of the irrigation system operate under the same conditions.

Understanding these two types is essential for selecting the appropriate regulator that aligns with the demands of a given irrigation system, making effective water management more feasible.

Other options such as variable and standard, high and low, or manual and automatic do not capture the primary categories of pressure regulators in a way that reflects their operational characteristics or design functionality in irrigation systems.