Irrigation: Sprinkler Valves

Though they are not always visible, sprinkler valves are an integral part of your irrigation system. They control and regulate the amount of water that each zone receives and may be controlled manually or electrically with a timer. In addition to regulating water flow, valves are also used to turn off your system in emergencies as well as prepare it for winterization. Different types and sizes are appropriate for different uses, so it’s important to know what to use and where to use it. You’ll also need to consider the best way to prevent backflow. Use the following questions to help determine what issues to keep in mind as you shop for valves:

• What types of sprinkler valves are available?
• What other types of valves are necessary to install?
• How large should valves be?
• What devices can be used to prevent backflow?
• How can you conserve water and ensure efficient performance?

Valve Types, Considerations and Backflow Prevention

Anti-siphon and in-line valves are both viable options. In addition to valves that control the flow of water, you’ll also need to install emergency shut-off valves and you’ll want to consider a drain valve. Size, flow control and whether a valve “bleeds” internally or externally are other important considerations. Beyond valve issues, you’ll need to choose a method to prevent backflow, which can taint your drinking water. While anti-siphon valves have built-in backflow prevention (also called cross-connection control), you may need or want to install additional protection. Local laws and regulations may dictate which types of valves and backflow preventers you can or cannot (or must) use, so be sure to consult them prior to installing your sprinkler system.

Anti-Siphon Valves: With built-in backflow prevention, these valves help ensure that your drinking water stays safe. They are fairly easy to install and may be either manual or electric. Anti-siphon valves are installed above ground, making them easy to maintain. They are most often made of PVC, but they may be constructed from brass or bronze as well. Use anti-siphon valves in areas where sprinkler lines are located under gardens and lawns where pesticides, weed killers and other chemicals are consistently used. They are available in both 3/4" and 1" sizes.

• Install at least 6" above highest sprinkler head, and be sure to consult local codes
• Install electric valves with automatic timers for more convenient use
• Manual valves can be retrofitted with an automatic valve adapter
• Check valves from time to time to ensure the opening is free of debris

In-Line Valves: Unlike anti-siphon valves, in-line valves are usually installed below the ground and do not feature built-in backflow protection. This type of valve is generally used in conjunction with a backflow preventer, such as an atmospheric vacuum breaker. Valve boxes protect them to provide greater durability. Their in-ground installation allows them to be located anywhere within the landscape without detracting from its appearance. A manifold is a group of in-line control valves that stem from the main supply line to provide easy access and maintenance.

• May be either manual or electric
• Generally constructed of PVC, but may be made from bronze or brass
• Angle valves move water at a 90° angle
• Globe valves are often used when pipe is placed at the same depth within a trench

Other Valves: In addition to valves that regulate the flow of water, there are a few other types of valves necessary for proper operation of an irrigation system. Emergency shut-off valves cut the water supply to all or part of the system temporarily to prevent damage or to allow for maintenance and repair. They may be either gate or ball valves. Drain valves are located at low points on the main and lateral lines and are used to drain water from the system to make repairs or for winterization in colder climates. Indexing valves connect to multiple individual zones to allow water to progress through each zone.

• Gate valves are economical and require multiple turns to turn off water
• Ball valves require only a quarter turn and provide durability for frequent use
• Disk and butterfly valves are other types of high-performance emergency valves
• Indexing valves may be required in some areas

Valve Considerations: Deciding how large a valve should be depends on your system’s flow rate. 3/4" valves are ideal for most residential applications where the flow rate is around 8-10 gpm (gallons per minute). If, however, the flow rate exceeds 15 gpm, you’ll probably want to use a 1" valve. Installing flow control will allow you to customize performance by ensuring that the right amount of water is used in each zone. If valves are activated manually, they may be done so using the manual bleed feature.

• Valve diameter does not necessarily need to match pipe diameter
• Flow control helps conserve water by preventing fogging and misting
• External bleed valves are ideal for flushing dirt from lines during installation and repairs
• Internal bleed valves vent water to the downstream side to prevent water from leaking

Backflow Preventers: When sprinkler heads operate, they sometimes create a vacuum that can cause water that has already been expelled to be sucked back in. This water, which may have picked up chemicals from pesticides, fertilizers and other lawn products, can filter back into your drinking water and cause illness. Backflow may be caused by pressure generated by equipment (pressure backflow) or pressure exerted upon water (back siphonage). Backflow preventers stop this from happening and, in many cases, are required by local codes and regulations. Use the chart below to explore a few different types.

Type of Backflow Preventer	Function	Points to Consider
Atmospheric Vacuum Breaker (AVB)	Opens a vent that allows air into the system to prevent siphoning; installs between the circuit valve and delivery device	Prevents back siphonage Most economical Must be installed above ground One AVB must be installed for each control valve
Double Check Backflow Preventer	Uses two spring-loaded, independently operating check valves to block backflow if water pressure temporarily drops	Prevents back siphonage and pressure backflow May be required in some areas May be installed underground Protects against pollutants but may not protect against contaminants
Pressure Vacuum Breaker (PVB)	Installs on the pressure side of emergency shutoff valve to prevent back siphonage	Prevents back siphonage Install prior to installing valves May not be suitable for drip irrigation systems Local regulations may prevent usage
Reduced Pressure Backflow Preventer (RP)	Features two check valves and a pressure differential relief valve that operates automatically; installs between two emergency shutoff valves	Prevents back siphonage and pressure backflow Requires larger up-front investment Highly effective and efficient Must be installed above ground

Features

Built-In Pressure Regulators: Valves with pressure regulators control the pressure level directly, rather than relying on a system regulator that may be too far away to effectively regulate pressure at far ends of the line.

Molded Bolt: Valves with the stud part of a bolt molded to their bodies will not fall off when removing the nut, meaning you won’t accidentally lose it in the wet, muddy ground nearby.

Internal Scrubbers: If you draw water from a pond or irrigation ditch, look for valves with scrubbers that automatically remove algae to prevent buildup from blocking the opening.