Drip Irrigation Valves & Irrigation Control Valves
What are valves used for?
Irrigation drip valves are used to create various watering zones in a drip irrigation system. This separation allows for different watering devices to be encompassed in a single system. By the opening and closing of a valve, each zone in your irrigation system can be watered according to the needs of that zone (such as pressure requirements or limitations, watering frequency or duration).
Why are valves important?
Valves allow for one system to be split into various zones. Why is this necessary? Not all zones in drip systems should be watered the same. Some zones may require devices with higher pressure, while other zones may require very low pressure
Additionally, a water source can only provide so much water at once. Often times in larger sprinkler systems, the water source cannot supply the volume of water needed to water the entire system at once. By creating zones, this ensures the water source is not overtaxed, and that each watering device is receiving the flow rate required for optimal performance. (To check the flow rate of your water source, here is our flow rate calculator).
Different zones can also be programmed to have longer or more frequent watering times, depending on the needs of each area. Below are examples of areas that should be in separate watering zones for various reasons:
How valves work
When idle, water flows into the inlet and fills the bonnet chamber above the diaphragm. The pressure from the water holds the diaphragm in place, keeping the valve shut.
First, an electrical signal is sent from the controller to the valve solenoid. The solenoid coil becomes a magnet, and pulls the plunger up into the solenoid. This allows the water in the bonnet chamber to flow through the outlet of the valve, decreasing the pressure above the diaphragm.
Now that the pressure above the diaphragm is decreased due to the water flowing out, the water from the inlet can then rise high enough to push the diaphragm up, which opens the valve, allowing continuous water flow through it.
Once the flow of electricity to the solenoid stops, the plunger drops inside the solenoid and the water stops flowing in the solenoid dump port. After the bonnet chamber water pressure above the diaphragm becomes high enough to offset the water pressure below the diaphragm, the valve closes.
Types of valves
There are three basic styles of control valves to choose from. The angle valve, anti-siphon valve and the globe valve.
Angle valves are typically buried, and are similar to globe valves in their recommended applications. However, the angle valve is constructed a bit differently. This type of valve features an additional inlet at the base of the valve. This feature creates a 90-degree angle between the inlet and outlet connections.
This allows for moderation of pressure, incase a pressure drop occurs within the valve. If pressure fluctuations are prevalent in your system, angle valves are going to be a better choice than standard globe valves.
Anti-siphon valves are designed with a backflow prevention device built into the valve and are available in 3/4” and 1” size. This is important if you are going to use fertilizer or other contaminants in your irrigation system. Backflow prevention is a must, as you do not want any contaminants flowing backward into your drinking water source.
Another difference from globe valves is that anti-siphon valves must be installed above ground and at least 6” higher than the highest sprinkler head. The elevation is needed to make sure the backflow prevention feature works correctly.
Globe valves are common in commercial landscape systems and are typically buried under ground inside a valve box. Globe valves come in many sizes; however, they are not available with internal backflow preventers. So while globe valves are less expensive than comparable anti-siphon valves you should consider the cost of having to buy a separate backflow preventer when designing your irrigation system, as backflow prevention devices can be expensive, but they are necessary to protect your water source.
Jar top valves are globe valves that have removed the need for tools when disassembling the valve. These valves feature a threaded bonnet, instead of one that requires screws to hold it in place. Just as you would open a jar by turning it to the left, the same is true for these valves.
Hence the name, “Jar-Top”, making it incredibly easy to get into the valve as needed. Closing it up is just as simple, just turn to the right until the threads stop.
One option to consider are the all-in-one valves that feature a built in filter and pressure regulator. These features are only available in globe valves, and can come in very handy if you want to avoid buying extra filters or pressure regulators.
An example of this is if you were running sprinklers on the majority of the zones, but needed to filter to a finer mesh or reduce and regulate the pressure for a drip zone. Many of the all-in-one valves filter to 200 mesh and regulate the pressure at the valve to 30 PSI or below, making them ideal for most drip systems.
It is recommended verifying the operating pressures and filtration requirements needed for specific watering devices, as these requirements vary across different devices.
Flow control handles are an option on angle, anti-siphon and globe valves. These handles regulate the flow of water through the valve when the valve opens (not to be confused with a manual on/off switch). Typically it is a stem connected to the top of the diaphragm that goes up through the top of the valve to the flow control handle. The flow control handle works by regulating how far the diaphragm opens and allows water to go through.
By reducing the flow of water through the valve, this also reduces the water pressure of that valve’s zone. This may make the difference in your ability to operate a valve correctly in your irrigation system vs. having to replace the valve.
Flow control can also be used to override the automatic open and close function of the valve if there is an emergency, such as the valve being stuck open. Should that occur, the valve can be manually closed, allowing you time to asses the problem.
To manually operate a valve, turn the solenoid a quarter ¼” turn, counterclockwise. You’ll hear the water start to flow so when you are ready to close the valve you will turn it a quarter turn clockwise. You do not need to overtighten the solenoid, you’ll feel it stop. Once the valve is closed you will hear the water stop.
Considering the minimal additional expense to purchase a valve with flow control is money well spent. Your irrigation system is safe in the event of a valve that is stuck open or a valve that is causing trouble due to too much water pressure.