Irrigation / Lawn Sprinkler System Valves – What Are They
Irrigation Sprinkler System Guide
Irrigation valves or lawn sprinkler valves are an essential component of lawn sprinkler systems. They control the flow of water in lawn sprinkler systems. Sprinkler system valves come in a variety of models, including below ground inline valves and above ground anti-siphon valves.
Lawn sprinkler systems may be manual or automatic. Automatic lawn sprinkler systems consist of the controller / timer, the sprinkler valves, the pipes, and the lawn sprinklers. Each valve controls a different zone, or area, of the lawn sprinkler system. The controller sends electric low voltage (24 volt AC) signals to the valves, telling them to open or close.
Sprinkler valves come in many different styles. Globe or angle irrigation valves work with a separate backflow preventer, and anti-siphon valves have the backflow preventer built-in. Rain Bird valves, Toro valves, Hunter valves, Irritrol valves and Weathermatic valves are all reliable, well-known products that, with proper maintenance, will last for many years.
Irrigation Valves – Types of Valves and What They Are Used For Shut-off Valves
Emergency shut-off valves stop the flow of water to the irrigation system. If repairs are needed to the sprinkler system valves or any other part of the irrigation system, the shut-off valve prevents the need to turn off the entire water system to the house or what ever else the water feeds.
Emergency shut off valve: You should install this sprinkler system valve as close to the water source as possible and should be the same size as the pipe you are installing it on. If you do not install this valve, you will have to shut the water off to the entire house when you want to make repairs or work on the irrigation line. You only need to install one of these shut off valves for your irrigation system and it will either be installed under ground in a valve box or in the basement depending on where your water supply connection is located.
If you are using a water meter from the city as your source of water, it is best to tee off the pipe coming out of the water meter (the one headed to feed the house) as close to the meter as possible and use the tee to start the water supply to the sprinkler system. In this case, you would install the shut off valve close to the tee on the line headed to feed the sprinkler system. Some people will put the tee close to the meter but then install the shut off valve just before the backflow device which may be installed on the side of the house. If you are in an area that freezes and you will be using the basement water supply piping as your sprinkler system water supply, install the shut off valve in the basement on the piping before the backflow device.
The most popular valves used for this purpose are the gate valve, ball valve, disc valve or butterfly valve. The gate valves are the most inexpensive and tend to NOT Close completely plus they are typically metal and corrode quickly making it difficult if not impossible to use. Your best bet is to use a PVC ball valve (highly recommended) since they are a more reliable choice. They close completely and they do not corrode or rust which means you should always be able to open and close them easily even when buried under ground in a valve box.
Control Valves (as known as Zone Valves)
Irrigation control valves are used to turn the irrigation system on and off and there are two different types to choose from:
1.) Globe and Angle Valves
2.) Anti-Siphon Valves
The globe and angle valves come in any size and are usually installed under the ground or in a vault or valve box. Since there is not a backflow preventer attached as part of the valve, you will need to add that separately. This is the most common type used in sprinkler systems. However, you may choose to use the anti-siphon valve, which comes only in 3/4- and 1-inch sizes and comes complete with a backflow preventer. The anti-siphon valve absolutely must be installed above the ground and must also be 6 inches higher than that of the highest sprinkler head.
Valves come in brass and plastic; the most common ones used today are the plastic ones. The brass valves will ultimately last longer if installed in the sunlight. Both types are reliable for an automatic system, but for manual systems the manual brass valve is the best choice because it lasts much longer. Valves today are fairly maintenance free.
As for pressure losses and valve size, the automatic valves should be sized based on the manufacturer’s flow range chart and will not necessarily be the same size as the pipe. However, it is more common that it will be the same size as the pipe it is installed on. A manual valve is much more adaptable than the automatic and you do not have to depend on electricity to power it, rather it is done manually, hence the name. A manual irrigation control valve needs to be either an angle or globe type with replaceable rubber seals and not the gate type as the gate valve is not made to be opened and closed regularly.
Above Ground Anti-Siphon Valves
Anti-siphon valves have a built-in backflow preventer to keep irrigation water from washing back into the household’s main water supply. Use Anti-Siphon valves in locations where the use of a pressure vacuum breaker (PVB) or double check valve is not required by city codes. Some areas of the country, such as in California and Arizona, require backflow prevention for every zone. Check your local city codes to determine what type of valves are required. The Anti-Siphon valve is a combination valve that has an atmospheric vacuum breaker and an electronic control valve all in one unit. It provides backflow prevention on every zone, saving costs by eliminating the need for a separate backflow preventer. Anti-Siphon valves are installed above ground and will prevent back flow if properly installed. Anti-Siphon valves should always be installed at least 6” above the highest head on the valve line, and should never have another valve installed further down the line from the main valve
Below Ground Inline Valves
These valves are often globe valves or angle valves. Inline valves are installed underground, protected by a valve box. Below ground inline valves require a separate backflow preventer, installed to meet local bylaws and regulations. However, the great thing about inline valves is that they are typically less expensive than anti-siphon valves and you can install them in the middle of each zone (or section) of your sprinkler system which keeps the pressure loss in the zone more balanced and uniform. Furthermore, you save money on pipe since you end up with one mainline traveling through your yard supplying all you valves instead of having multiple runs of pipe in the same trench heading from the anti-siphon valve manifold to each zone. Plus you only need one backflow preventer device protecting the whole sprinkler system instead of paying for one on each anti-siphon valve. Using a single backflow device with inline valves is a better way of installing your system and it will last longer than the anti-siphon valve plastic backflow device which relies on gravity and has no other parts to assure it functions properly. One other important note: anti-siphon valve back flow vales can not be tested to see if the backflow prevention is functioning, however, backflow devices purchased separately to be used with inline valves can be tested to assure they are functioning correctly. Using inline valves is a more professional way of installing your sprinkler system.
Globe valves once had a spherical body, but modern globe valves have changed in shape, and only the name remains. Water flows through the valve without changing direction. The two halves of the valve body are separated by an internal baffle. A movable plug, or disc, screws in to shut off the valve. In manual globe valves, the plug connects to a stem which operates by hand wheel. In automatic globe valves, the stem is smooth.
Named for their angular design, angle valves direct the flow of water at a right angle to the valve. Water flows into the valve, then changes direction 90%.
The Valve Manifold
The manifold is a group of control valves attached to a pipe. Water enters the manifold from the main water supply line. The water is then routed through the control valves. The valve manifold may be below or above ground.
To build the valve manifold, use a length of PVC pipe. Space the valves about three to six inches apart. The number of valves determines the overall length of the manifold pipe. Include an extra connection or two, for possible expansion to the system later. Save time and work by purchasing a ready-to-install manifold kit, which includes the sprinkler valves and all necessary parts and instructions. Many manifold kits have a flow control feature, to help conserve water.
A valve box is a plastic cover that protects the valves and wiring from damage and debris. Above ground, the valve box also protects the valves and manifold piping from harsh sunlight and inclement weather, or damage by accident, animals or vandalism.
Backflow Prevention Devices
Backflow prevention devices will prevent irrigation water from lawn sprinkler systems from backing up into the drinking water. Irrigation water may contain contaminants such as pesticides and other chemicals, as well as waste products and dirt. While these elements don’t harm the lawn, they create health risks in public or household drinking water.