Water pipes form an underground maze, with offshoots from main lines creating a complicated, submerged city map. Irrigation systems add twists and turns to these pipes -with every corner and cul-de-sac water can gather impurities that could be dispensed back into the city's system.
Backflow prevention devices ensure that water that enters property pipelines does not return to the municipal water supply. "Once water goes through the meter, it will go through the backflow preventer and not enter back into the water purveyor's lines," described Jon Everett, technical services manager, Wilkins Operation, a division of Zurn Industries, Casa Robles, Calif. "We want water to go in, but we don't want it to go out," he said, simply.
This is mainly because water that "goes out" might not be free of debris, whether contaminants are hazardous, like fertilizer, or merely displeasing, like grass clippings or dirt added Scott Knowles, president, Wolf Creek Co., Dayton, Ohio.
"Cross connection is the key word," he stressed, adding that irrigation systems fall under this category because their connections tap into the city's water supply lines. "The first thing that has to happen is to install a backflow prevention device before any other device is installed on that piping. That prevents any contaminants from getting back into the service line for that city's main line."
Before installing irrigation systems, contractors must consider possible backflow conditions, reference state and city laws and then choose the backflow assembly to prevent contaminating potable water.
GO WITH THE FLOW. Different backflow conditions call for different prevention assemblies, so contractors must assess a property's water pressure before choosing the appropriate device, Everett noted.
Backsiphonage and backpressure prompt pressure imbalances between the city and property pipelines that can result in the release of contaminated water into the municipal system. The former occurs when the city water pressure drops, the latter when a property pipeline loses pressure. Both cause the line with the most pressure to overcompensate and force potentially contaminated water into the main lines.
Backsiphonage is like siphoning the water out of your house," Everett compared. If there is a break in a city line and the pressure drops, water will suction from the property pipe with more pressure to the municipal pipe.
On the other hand, if a property's pipeline pressure is greater than that of the main line, water can be pushed back into the municipal line. Jeff Keim, president, Backflow Prevention Device Inspections, Phoenix, Ariz., said backpressure on an irrigation system commonly occurs in three ways: from a pump on the system; from gravity when one part of the system is on a higher elevation than the vacuum breaker; or when two or more incoming water lines supply the system.
Louis Toth, owner, Aqua Lawn, Fairfield, Conn., also listed well failures as a pressure risk. "If you have a break in the line and the pump is not running, water can seep back into the well," he described.
Backflow prevention devices serve as a precaution should these situations arise. "If there is a sudden loss of pressure and water flow backward, pulling debris into the line, the backflow prevention device will stop it so nothing from the property can get pulled past that point - dirt, nematodes or pet waste," Knowles explained.
THE GENERAL ASSEMBLIES. Most states require backflow prevention devices, however, some regulations are more strict than others. And some cities within these states apply further stipulations, limiting installation to certified technicians or plumbers. Regardless, contractors need to know the rules and stick to government guidelines, Keim stressed.
"There is still some level of controversy in the industry as to what level of protection is needed, but more and more people are erring on the side of caution and stressing the high-hazard assembly equipment," he noticed. Each assembly caters to different pressure and health hazard levels.
To avoid ineffective systems due to mismatching backflow prevention devices, contractors should understand available assemblies, Keim emphasized.
"One of the mistakes that contractors make is using the wrong assembly in the wrong circumstance," Keim added. "The different assemblies have different uses."
For example, complicated loop irrigation systems involve interconnected feed lines that are under pressure, requiring a reduced pressure assembly. "A pressure vacuum breaker would cause each feed line to backpressure one another, so you could have a constant problem where water enters into the system at one point and exits at the other backflow assembly, literally flowing through it."
The versatility of reduced pressure assemblies makes them an attractive option for many contractors, including Toth. Licensed plumbers install prevention assemblies for his company, and by choosing this particular device he feels he is taking utmost precaution. "It's a must that we use some sort of device, and in Connecticut, for instance, everyone is alert and very cautious about how we install sprinkler systems," he said.
Each prevention device comes with installation parameters. For example, pressure vacuum breakers must be installed 12 inches higher than the highest outlet on the downstream piping, Knowles specified. "For example, if the water tap is in the front yard and the backyard goes uphill and there are sprinkler heads there, too, then the pressure vacuum will not do its job," he explained.
Reduced pressure assemblies are ideal for most properties, including those with slopes, Knowles added. Here, the contractor does not have to worry if one sprinkler head rises above another because of the land grade.
INSTALLATION TIPS. Besides noting health-hazard potential and minding installation measurements, contractors need to watch out for other common installation mishaps. This includes making sure the devices are not installed in areas that flood, Knowles noted. "Water will squirt out of the device when it is doing its job, which means it has to be placed in an area where water squirting out won't hurt anything, or where the water can be collected and sent to a drain," Knowles said.
Assembly placement also depends on the region, he added. Contractors in warm climates might choose to tap pipes outside, while cold states might install devices indoors. Contractors should also set prevention devices at least 8 inches away from walls, so they are accessible for inspections and repairs.
In addition, Knowles suggested installing backflow prevention assemblies on copper pipe instead of polyvinyl chloride plastic pipe, which cracks easily under pressure. He recommended sizing the device to match the flow - using a ¾-inch assembly for a 1-inch pipe, for example. "Most of the time, the backflow prevention device does not have to be the same size as the piping, especially in low-pressure areas," he noted.
And by ensuring that check valves inside the device are free of debris, contractors will avoid making trips to the distributor for replacement parts, Knowles said. "Many times the contractor says the device isn't working right, and debris lodged inside is the culprit," he pointed out.
For piecing together piping, Keim advised using Teflon tape instead of pipe dope, which can come loose, enter the assembly and cause it to malfunction. When installed, relocated or repaired, a licensed or certified backflow prevention expert should test the device, he stressed. "Working on a backflow assembly and not having it tested creates a legal liability on the part of the contractor," he said.
Despite details associated with installing the devices, "they are not a necessary evil," Everett pointed out. "They are meant to save lives."
Blocking potential contamination that can cause water to smell, look unappealing or pose health risks is a civil responsibility, Knowles added. "It's being a good neighbor, when you think about it," he said.
