Like the AVB it must be installed 6 inches mm higher than the highest sprinkler head or drip emitter outlet. If you install any valves, of any type, on the pipes downstream of the anti-siphon valve, the anti-siphon valve will not work! It may not be installed in any location where it might ever be submerged under water.
Anti-siphon valves are the most common type of backflow preventer used on residential irrigation systems, primarily because they are simple and inexpensive. Some municipalities do not allow the use of anti-siphon valves, so it is best to check with the water company first. Generally you would install the anti-siphon valves in one or more groups, at the highest point in the area to be irrigated.
A mainline pipe is run to the anti-siphon valve location s from the water source. Pipes then extend from each anti-siphon valve to the sprinklers or emitter tubes. Because anti-siphon valves must be installed at least 6 inches mm above ground, it is a good idea to put a small planting of shrubs around them to help hide them from view. They are not particularly attractive! Water may come out of the anti-siphon valve periodically, so make sure you install them someplace where a little spilled water will not be a problem.
The water will come out of the vent, which is under a cover on the top of the downstream side of the valve you can see the vent holes under the cover if you turn the valve upside down and look for them. If water does come out of the anti-siphon it means something is wrong that needs to be fixed.
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In most cases it means either a stick or rock got into the anti-siphon seal and jammed it open, or the anti-siphon valve was not installed higher than all the sprinkler heads or emitters. Anti-Siphon Valve Installation Detail. Pressure Vacuum Breaker. A pressure vacuum breaker PVB is similar to an atmospheric vacuum breaker except that you only need to install one of them and it is installed on the mainline leading to the control valves. Like the AVB it must also be installed above ground and it must be 6 inches mm higher than the highest sprinkler head or drip emitter controlled by any of the valves.
In a sloped yard it would typically need to be installed at the highest point in the yard, with a mainline pipe running up to it from the water source, and then another mainline running back down to the control valves. Some municipalities do not allow the use of PVBs with drip irrigation systems. A PVB backflow preventer may spit or spill water out from under the cap when backflow occurs, so it should be installed in a location where water spillage would not cause problems. Warning: If used on a water system where a pump and pressure tank supplies the water like is used on most rural homes that have a well , the PVB may spit water each time the pump shuts off.
This is because the pressure variations caused by the pump and pressure tank system can cause backflow from the irrigation system back into the water system. The likelihood of water spitting, and the amount of water that spits out, both increase with a longer mainline on the irrigation system. So if you have 10 feet 3m of mainline between the PVB and the farthest valve there is less likely to be water spitting than if you have feet m of mainline pipe.
One way to stop, or at least reduce, this water spillage is to install a spring-loaded check valve right after the PVB. The PVB may still spill a little water with the check valve installed, however in most cases it should be much less water. Reduced Pressure Backflow Preventer. The reduced pressure backflow preventer R. Unit is the king of the backflow preventers, made for high-hazard uses. It is also an expensive piece of equipment. It is the standard for commercial irrigation installations. This is the type of backflow preventer that I use on most of my designs.
The R. Unit must be installed 12 inches mm above ground, but it does not have to be higher than any of the sprinklers. If installed in a structure or basement there must be a drain located near the backflow preventer. A single R. Unit is installed upstream of all the valves.
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Units are used for many things other than irrigation systems. Drive through any commercial business area and you will likely spot a lot of these units, most often sitting right out by the street. Many times you may see several grouped together, each used for a different purpose.
Double Check Backflow Preventers. Depending on who you ask, double check backflow preventers may or may not be appropriate for irrigation systems. In many communities they are legal to use, and even recommended by local officials. Other communities do not allow them to be used on irrigation systems. I will attempt to present both sides of the argument. Dual check backflow preventers are for use with non-toxic materials.
The water in your house is hopefully! How do you recognize which is which when you see them? These manual valves are used as emergency shut-offs and are also necessary to properly test the operation of the backflow preventer. A Double Check will also have test cocks small outlets sticking out of the side of the backflow preventer for connecting to test gauges. Many communities that allow double check backflow preventers do not allow the use of dual check backflow preventers. For more on dual checks, click here.
A double check backflow preventer is simply two spring-loaded check valves in a row, with a shut-off valve on either end and test cocks to allow the unit to be tested for proper operation. The double check backflow preventer is the only true backflow preventer which does not have a vent to allow air to enter the lines or to allow water to escape when backflow occurs. It relies entirely on the tight seal of the two check valves to prevent backflow. In most places where double check backflow preventers are legal, local officials will allow them to be installed underground in a vault.
However, since not all do, you should always check with local officials before installing the unit underground. Double check backflow preventers can be installed lower than the irrigation system and often they are installed in basements in order to protect them from freezing. Regardless of where they are installed they must be readily accessible for maintenance and testing.
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Even in areas where double check backflow preventers are approved for use they may not be used on any irrigation system where chemicals fertilizers, pesticides, fungicides, pipe cleaning agents are injected into the irrigation water. For an explanation see my separate article with an in-depth discussion of the pros and cons of double check backflow preventers.
Dual Check Device.
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Technically this one is NOT a backflow preventer. It is essentially a stripped down version of the Double Check Backflow Preventer, without the shut-off valves or test cocks. What are they made for then? Just to confuse people? It may seem like it! What they are is a flow control device rather than a backflow preventer. Now I admit there is a thin line of difference between the two. OK, to set the record straight, I have heard that some authorities do suggest the use of these devices as backflow preventers.
In most cases they are requiring them in locations where the general consensus is that no backflow preventer is needed at all. Most municipalities do not require backflow preventers on water supplies to single family homes, provided water is only used for drinking. The authorities assume that your toilets, washing machines, bathtubs, and dishwashers all have built-in backflow preventers- which pretty much all of them do.
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However, some authorities apparently are allowing, and even recommending!!! Then to save even more money, they decide to leave out all the test equipment used to confirm that it is not overheating or leaking radiation? Only Homer Simpson could get excited about that! All of the following backflow preventer types are available in several sizes. All backflow preventers must be installed correctly.
Follow the instructions that come with the units. Backflow preventers should be checked yearly for proper operation. In areas where it freezes, the backflow preventer should be protected from freezing. See the Irrigation System Winterization tutorial for details. This page is linked into several of the tutorials. This website is intended for use by residents of North America only. This website uses both first-party and third-party cookies. By continuing you agree to the use of these cookies or other local storage, as well as the collection, sharing, and use of personal data for personalization of ads or other services.
I agree. We recommend drawing your plan to scale, ie. This will make it much easier when calculating sprinkler spacing and pipe lengths. For PVC Pressure systems, we recommend connecting directly to the water mains in most cases. When running irrigation system off the main line, an irrigation controller is required. Without a flow meter, this can be measured with a Bucket Test, by timing how long it takes to fill a household bucket.
This can be measured off a household tap or directly from the main water feed. If measuring directly off the mains, you may want to consult a plumber. Note that the fill time needs to be calculated at full flow and mid-stream, so the bucket must be placed under the tap after it is already running. Pick the Right Sprinklers With the area layout planned, we can now map our ideal water coverage, using fixed and adjustable nozzle sprinklers. Find your nearest Store. A solenoid valve is essentially an automatic tap. Using a magnet within the solenoid coil, the valve can be turned on or off remotely via an irrigation controller.
By utilising solenoids in an irrigation system, watering in multiple sections or zones can be controlled from a single irrigation controller at a central point. These valves are controlled by a safe 24V AC current, passed from the irrigation controller which is wired directly to the solenoids. Why do I need Solenoid Valves? Rule of thumb: The larger the irrigation area, the more solenoids required After selecting your sprinklers and determining the system flow rate, you can then determine how many sprinklers can run at any one time In most cases, it is not possible to run the entire system of sprinklers because you will not have enough water, so we divide the system into zones, which are then controlled by solenoids.
Which Solenoid Valves should I Choose? Heavy duty and corrosion resistant with flow control. The only choice for connecting to the main line. Browse KR Master Valve. Easy to service with a 5 year warranty, our Jartop Valves are corrosion and UV resistant. Browse Smart Irrigation Control. The essential solution for controlling irrigation, the Holman Dial Ezy range of controllers is perfect for residential applications. Plot your Pipework. For optimal flow, sprinklers should be connected in the shortest possible chain, as the water pressure is reduced every time it passes across an opening.
See also: Flushing your Irrigation System. If your system is to be automatic, you may require a licensed electrician to connect your automatic controller.