Brian Vinchesi, principal of Irrigation Consultants, Inc., in Pepperell, Massachusetts, and past president of ASIC asserts that along with the criteria for choosing a backflow prevention device, you need to address the local regulations as well.
Most regulatory bodies provide these guidelines and should be consulted before selecting a backflow prevention device for a project, so the only thing left to decide is what type of backflow youre protecting your system from and what would be the most appropriate form of backflow protection, he asserts.
Although commercial backflow prevention regulations seem pretty consistent, at least in their guidelines and requirements, residential backflow regulations vary widely from jurisdiction to jurisdiction.
Commercial backflow prevention regulations are pretty solid and enforced, offers Brad Noll, engineer manager for Wilkins/Zurn in Paso Robles, California, But regulations for residential properties really need some work. We regularly see poor installations and little to no testing and inspections.
However, the landscape industry is gradually moving toward more protection at the residential level, Noll continues, from atmospheric vacuum breakers to pressurized double check valves and RPs.
Although jurisdictions are increasingly codifying backflow prevention for residential applications, it appears that for now, responsible specifications are up to the industry. A mandate for requiring specific backflow prevention devices at the residential level is one thing, but enforcement is quite another, Noll asserts.
Backflow Prevention Devices
There are five primary types of backflow prevention currently accepted in most states:
1.) The Air Gap is a physical separation between the free-flowing discharge end of a potable water supply pipeline and an open, non-pressurized receiving vessel. The separation between pipe and tank is twice the diameter of the piping and no less than one inch. This method is approved for high hazard.
2.) A Reduced Pressure Principle Backflow Prevention Assembly (RP) contains two independently acting check valves with a pressure differential relief valve between them. The units also have two shutoff devices one upstream and one downstream of the check valves. This assembly is approved for high hazard situations, backsiphonage and backpressure.
3.) The Double Check Valve Assembly consists of two independently acting check valves. These units also have two tightly closing shutoff valves located at each end of the devices. This assembly is approved for low-hazard, backsiphonage and backpressure.
4.) A Pressure Vacuum Breaker (PVB) employs an independently acting, spring-loaded check valve and an air-inlet valve that opens to admit air when the pressure within the body of the device approaches atmospheric pressure. This assembly is approved for high-hazard backsiphonage.
5.) An Atmospheric Vacuum Breaker (AVB) consists of a check valve and an air-inlet valve. This assembly is approved for high-hazard backsiphonage.
Evolving Codes and Regulations
Remember that any mechanical device can fail. To ensure these mechanical devices are working properly, they must be tested regularly.
|Keeping backfkow devices locked prevents vandalism.|
Local and state regulations regarding cross connections must be followed regarding the selection, installation and testing of the approved backflow prevention device. Each state and many municipalities have varying regulations and codes, so not all states approve the same devices for the same conditions.
How do you know which backflow prevention device is appropriate for your project? Some jurisdictions follow all or parts of the Universal Plumbing Code and the International Plumbing Code, but these are just guidelines, offers Dale Strong, president of the American Backflow Prevention Association. The safest way to ensure you are selecting the proper backflow prevention device is to first contact the water supplier to that project, Strong adds. Codes and regulations vary widely across the country and even from municipality to municipality.
Vinchesi agrees: Backflow prevention devices cant really be over- or under-specified; its all codified. You specify what the codes say according to your site parameters. The rules are pretty much cast in stone, he adds. The problem is when the local inspectors dont know the law. Perhaps a second opinion is in order if you have questions after a meeting with the backflow prevention inspector.
The selection of the proper backflow prevention device obviously is important, but having the apparatus for the cross connection isnt enough it also must be installed correctly and inspected regularly.
For example, these devices should not be placed in locations that could become subjected to localized flooding. Few jurisdictions allow the installation in a pit, unless the pit is waterproof. Installation of these devices should also require clearance for testing and servicing.
RPs and double checks require a minimum 12-inch clearance above the grade to ensure an air gap between the relief valve and any water that could pool beneath the devices. The PVB cannot be installed where there could be backpressure only backsiphonage and must be installed at least 12 inches above the highest sprinkler system outlet.
Just like the PVB, an AVB cannot be installed where there could be backpressure, only where there could be backsiphonage. The AVB must be installed at least six inches above the highest system outlet and cannot be under continuous pressure.
It is important to understand that backflow prevention devices are designed to protect our potable water supply from pollutants and contaminants. Become aware of the requirements and local codes for backflow prevention protection.
Backflow prevention is a public safety issue that is not always understood or addressed in irrigation designs and installations, adds Dan Benner, president of the American Society of Irrigation Consultants. An important part of an irrigation consultants role on a project is that the appropriate equipment is functioning properly at the finish of an installation. Were the clients safety net for compliance.
The American Society of Irrigation Consultants (ASIC) was formed in 1970. For more information about ASIC or its members, call 508/763-8140 or visit www.asic.org.