Sometimes called a check valve or a backflow preventer, a chemigation valve is an apparatus designed to protect water supplies from
agricultural chemical
An agrochemical or agrichemical, a contraction of ''agricultural chemical'', is a chemical product used in industrial agriculture. Agrichemical refers to biocides (pesticides including insecticides, herbicides, fungicides and nematicides) and sy ...
s used during
chemigation, the application of chemicals such as
fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
s and
pesticide
Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...
s through
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
water. Most chemigation valves consist of a spring-loaded
check valve
A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.
Check valves are two-port valves, meaning they have t ...
, a low pressure drain, an air and vacuum relief valve, and an injection port for introducing the chemicals downstream of the check valve. Many chemigation valves also have a 4-inch inspection port so that a person can reach inside and feel if the check valve is still functional. Some governments require the use of two chemigation valves installed in series if hazardous chemicals are to be injected.
The following policies require or encourage the installation of these valves:
Texas State law Chapter 344.73 in Subchapter D - 1.(b)
: "An irrigation system which adds any chemical is considered to be a 'high health hazard'. Such an irrigation system must not be connected to any
potable water
Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ag ...
supply except through a reduced pressure principle backflow prevention assembly."
Florida's Department of Agriculture and Consumer Services Water Quality/Quantity Best Management Practices for Florida Specialty Fruit and Nut Crops
p. 20 specifies that:
: "Backflow prevention should include a check valve between the irrigation pump and the injection device to prevent backward flow; a low-pressure drain to prevent seepage past the check valve; a vacuum relief valve to ensure that a siphon cannot develop; and a check valve on the injection line."
See also
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Air gap
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Hydrostatic loop
A hydrostatic loop, though not often used in plumbing practice, is an arrangement of pipes formed into a vertical loop to prevent backflow of water within the plumbing potable water system. Since a siphon has a maximum height that it can work ( ...
*
Pressure vacuum breaker
A pressure vacuum breaker (PVB) is a type of backflow prevention device, used to keep non-potable (or contaminated) water from entering the water supply. A PVB is similar to an atmospheric vacuum breaker (AVB), except that the PVB contains a sprin ...
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Double check valve
A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination. It is different from the two-way check valves (sometimes erroneously referred to as double check valves) u ...
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Reduced Pressure Principle BFP
A reduced pressure zone device (RPZD, RPZ, or RPZ valve) is a type of backflow prevention device used to protect water supplies from contamination. RPZDs may also be known as reduced pressure principle (RP), reduced pressure principle backflow ...
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Atmospheric vacuum breaker An Atmospheric Vacuum Breaker (AVB) is a backflow prevention device used in plumbing to prevent backflow of non-potable liquids into the drinking water system.
It is usually constructed of brass and resembles a 90-degree elbow with a hood on it ...
References
Plumbing valves
Irrigation
Backflow
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