Irrigation System - Backflow Valves

When installing an irrigation system - backflow valves are a necessity, preventing contamination from entering the system.

Backflow usually happens when water at a higher elevation flows through a cross-connection in the system at a higher pressure, or when "backsiphonage" occurs – water is siphoned back into the main supply due to undersized pipes or reduced perssure because of line breaks.

When installing your type of irrigation system, you'll want to install backflow valves to protect your drinking water. Backflow can cause unwanted chemicals from your lawn or garden to enter your water supply, contaminating your drinking water.

The kind of backflow preventer you choose to install depends largely on the chemicals you're trying to keep out of your water supply. of any substance which can flow into the potable water supply. Your home irrigation system is considered a "moderate hazard" system, with your contamination risk coming mainly from the fertilizer in your lawn, pool chemicals, or backflow from submerged sprinklers. An industrial site that uses pumps to add fertilizers or other chemicals directly to the water supply is considered a "high hazard" system.

For your home system, check first with your local water bureau to get a list of approved backflow prevention devices. In most cases, you'll have a choice of four types of backflow assemblies: RPBA (reduced pressure backflow assembly, which allows the user to add fertilizer or chemicals to the system – it's also the most expensive), DCVA (double check valve assembly, a good, versatile home option), PVBA (pressure vacuum breaker assembly, which protects the entire system with one valve assembly) or AVB (atmospheric vacuum breaker, the least expensive, but designed so that no secondary on/off valves can be installed downstream from the backflow assembly).

A small amount of research into these different backflow assemblies will tell you which is right for your needs. Check with you're your local water authority to find out if you need permits to install your home irrigation system, backflow valves that they recommend, and any tips they can offer on home irrigation.