The 3/4" FNPT plastic back-flow preventer (anti-siphon valve) from Hendrickson Bros is an effective and economical way to eliminate the risk of back-flow contamination from an outdoor pipe or other water outlet with pipe threads. Constructed of high-strength ABS plastic the back-flow preventer is made of corrosion resistant material with outstanding reliability and long life. The devises are laboratory tested and industry approved since 1984.
The 3/4" plastic back-flow preventer (anti-siphon valve) from Hendrickson Bros is available in 3/4" with female hose thread or pipe thread. The back-flow device is installed at the beginning of a drip irrigation system and is used to prevent water from back siphoning into the water supply line. The back-flow device should always be used when applying fertilizer and when applying fertilizer the back-flow device should be the first item installed after the faucet. Install it with a pressure regulator with hose or pipe thread.
Important: This type of back-flow device (vacuum breaker) cannot be used under continuous pressure.
Codes do not permit the use of this device under continuous pressure as the back-flow device can stop functioning in emergency conditions. If used under constant pressure, the back-flow device can crack and fail due to a pressure surge when downstream valves close. Some municipalities or local water districts require the use of back-flow device/atmospheric vacuum breakers. Make sure to check your local city code to see if you need to install this device.