Backflow Prevention Guide

What is backflow, and why is prevention important?

Backflow is defined as the flowing back of liquid opposite the desired direction or the return of liquid to its source.

What does it mean in regard to irrigation? Typically, your irrigation water is connected to a yard spigot, which is fed by the main water supply. This could be your municipal source, city water, well, or spring. You could pull your irrigation water from a stream or pond. With any of these sources, having water from your irrigation lines siphon back into your water source could be dangerous.

Your emitters are typically near the ground in a drip system, possibly under mulch. When the system shuts down, a suction effect occurs, and dirt particles or other debris can be suctioned back into the emitter and make its way into your water source. Suppose you inject anything into your irrigation system, such as fertilizer or any other nutrient or chemical. In that case, a backflow device stops the siphon and keeps anything from contaminating your water source.

Many counties require a backflow device on any irrigation system, regardless of whether anything is being injected into the water. There are several types of backflow, the most common being a simple air gap. Think about your sink. The sink has an air gap, preventing water from returning to the water source once you turn the water off. This does not apply to your irrigation system because you will not disconnect your hose or irrigation line from the water source at every shut-off.

Three other popular options would be a hose bib vacuum breaker, a single check valve, or a double check valve.

A Hose Bib Vacuum Breaker is a simple unit that attaches to your hose-threaded system to protect the water source. Vacuum breakers are not rated for constant pressure, and they do have pressure and flow restrictions. The highest incoming pressure a vacuum breaker can handle is 100 PSI. They have a maximum flow rate of 8 GPH; you will lose 10 PSI through the unit and full flow. Depending on what you inject, this inexpensive backflow solution may not meet county code regulations, so please check your codes to ensure you are using the correct backflow prevention.

Single Check Valves come in female pipe thread ranging from 3/4" up to 2" to fit your system's size requirements. A Check valve has a built-in spring that only allows water to flow in one direction. This type of backflow prevention is a little more robust than a hose thread vacuum breaker but may not meet specific county codes.

Double Check Valves are the top-notch, safest backflow device you can get. These units are made of lead-free brass and have two check valves for fail-safe operation in preventing any contaminated water from re-entering your water supply. This type of check valve protects against back-siphonage as well as backflow.

Backflow prevention doesn't have to be complicated to understand with the correct information at hand. For more detailed information or questions, please try our Live Chat or call us at 1-800-522-3747 Monday through Friday from 8 am-4 pm PST.