The two questions – next steps

With the primary function and the control decided, the next step is to decide the specific parameters of the valve.

This includes whether plastic or metal, the size, and the connection type. You will also decide the exact pilot and solenoid required.

Plastic or metal is generally a personal preference for the application. Plastic valves are lighter, easier to install, more economical, and do not have the risk of corrosion. However, they are not as strong and are available in fewer models, including only smaller valve sizes. They are generally used as block valves.

Metal valves are generally required for the main control head due to the larger size and higher pressure requirements.

Connection type is defined by the region of the farm (the standard for the country) and the application.

Size is the main determinant of possible flow, and needs to be considered with the flow and the head loss of each valve, the details of which can be found in the relevant Rivulis product literature.

Pilots regulate the pressure of the valve, e.g. ensure the correct downstream pressure for pressure regulating valves.

This regulation is achieved by balancing the forces on the operational elements. To put it another way, pressure is applied to the diaphragm in the control chamber of the valve. The degree of pressure determines how far the valve opens, i.e. pressure regulation.

The image below shows a PR/PS valve (therefore two pilots). What occurs is:


  • The PR pilot receives water pressure from downstream of the valve.
  • The PS pilot receives water pressure from upstream of the valve.
  • The two pilots control the pressure within the regulation chamber by applying water pressure to the diaphragm in the valve.
  • Regulation is achieved 100% by the balancing of forces by pressure.
  • The balance is determined by the settings of the pilot.


A pilot will have a pressure range, and generally a preset, e.g. a range of 0.3–2.5 bar (4–36 psi) and a preset of 0.8 bar (12 psi) for a low pressure application.

Different pilots have different ranges and presets.

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