Today, August 16, is National Backflow Prevention Day. This new event created by Watts Water Technologies, is “a day dedicated to the celebration of backflow prevention and cross-connection control. Backflow preventers are the unsung heroes of water safety as they often go unnoticed, yet play a crucial role in supplying clean and safe water.”
Irrigation systems maintain the health of turf and plants in a landscape but can also improve human health and safety. Keeping potable drinking water separate prevents contamination that may cause illness or even death.
According to the Uniform Plumbing Code, an irrigation system must have an approved backflow prevention device to prevent pollution or contamination of public water supplies. However, there are different types of devices, and you might choose one over another depending on local laws and the specific application. Here are the four main types of backflow prevention devices as well as their advantages.
Double Check Valve Assembly (DCV)
As the name implies, a double check backflow preventer has two valves and is the most common way to prevent backflow. This type of device features two spring-loaded check assemblies inside an enclosed body with 1-pound springs that hold the check valves closed if backflow occurs.
While they’re used to prevent back siphonage and back pressure, this type of device is best for low or non-health hazard systems and is not recommended for high-risk situations like an irrigation system with a fertilizer injector. The advantage of this type of backflow preventer is the ability to install it in a valve box underground.
Pressure Vacuum Breaker (PVB)
For a device that specifically prevents back siphonage, a pressure vacuum breaker can be used. It cannot prevent back pressure, but it does have a spring-loaded check valve that will close whenever water stops flowing with an air relief valve that opens to break the siphon when pressure drops to 1 PSI.
While this device has to be installed 12 inches above the highest emission point, it has the capacity to be installed with multiple zone valves in valve boxes underground. If it fits the type of project you’re working on and meets local regulations, this device is a more affordable alternative to the double check valve assembly.
Dual Check Valves
Designed for installation on water lines to protect against back siphonage and back pressure, these relatively small devices have two inline check valves. Like the double check valve assemblies, dual check valves only provide protection where a potential health hazard does not exist.
This type of device has no ports and can’t be tested during an irrigation audit so check local regulations ahead of the install. They are easy to install on existing services and can typically be configured with union fittings on both the inlet and outlet sides.
Reduced Pressure Assembly (RP or RPZ)
The only mechanical assembly allowed for use in high-hazard applications like commercial sites or fertigation systems is a reduced pressure assembly or reduced pressure zone. With back pressure prevention, this type of device provides the highest degree of protection and is rated for high-risk situations.
This device has a pressure differential relief valve in a zone between two spring-loaded check valves, which can discharge water to reduce pressure. Like the double check valve assembly, they don’t need to be installed at a higher elevation than sprinklers and other emitters. However, this backflow prevention device reduces water pressure by about 10 to 14 PSI as the water passes through it so be sure to take that into consideration when you layout the irrigation design.
Incorporating a backflow prevention device into an irrigation system helps to maintain a safe water supply and prevent potential health hazards, which is a great reason to celebrate this new national day. For more information about National Backflow Prevention Day, visit the Watts Water Technologies website, and check out the hashtag #backflowday on social media if you’d like to follow the conversations happening online.
Trivia time: Can you name a fifth type of backflow prevention device typically used for siphonage? Share your answer in the comments below.