When it comes to different backflow devices there are several to choose from. While they all function in keeping the water you use in your home clean, the type of device you may require will depend on what kind of water backflow situation you need to prevent. Here is a small list of a few popular ones with detailed explanations.
1. Atmospheric Vacuum Breaker
This is an elbow-shaped device bent at a 90 degree angle. There is a valve on the inside of it that prevents water backflow. The system is based on pressure and should be installed at least six inches of where the downstream will be. It can be placed on PVC pipes, but is not testable.
2. Chemigation Valve
This type of valve is used on agricultural areas. It is meant to keep the local water supply clean in the presence of various farming pesticides, fertilizers, and other chemicals. The use of these products is called chemigation. There are several components to this valve. The check valve has a spring operated flapper, which allows flow in only one direction. There is also a low pressure drain and an air vacuum release valve in the device. The last component is the injection port. This is where the chemicals are introduced to go downstream of the check valve.
3. Hydrostatic Loop
When pipes are arranged into a vertical form it is referred to as a hydrostatic loop. In this configuration the loop must be higher than 33 feet to function appropriately. When designed this way it prevents siphoning and backflow into a water system.
4. Double Check Valve
This type of valve is typically seen on lawn sprinkler systems or fire sprinkler systems. There is a ball valve or gate valve assembled on each end. This allows for isolation and testing. Normal and reverse flow is possible with this valve.
5. Reduced Pressure Zone Device
This device, abbreviated RPZD, is also very effective in preventing contamination of water supplies. Unlike other devices, it is designed for high level hazards. A high level hazard is defined as a situation in which the water backflow could seriously harm individuals. In some cities, these valves must be tested once a year by a certified technician. The device has a chamber between two independent check valves where pressure is monitored. Excess pressure is relieved through an additional drain, while the monitor chamber remains at a lower pressure than the water supply pressure.
6. Air Gap
This last prevention device is something found in almost all homes. It is the faucet in your home where there is a literal air gap between the faucet head and the sink itself. During ice freezes in the winter, people are advised to turn the water on at night. The movement of the water prevents it from freezing, expanding, and bursting the pipes. It also relieves pressure by allowing the water a place to go if pressure builds in the pipes from partial freezing.