Essential Guide to Backflow Freeze Protection for Your Irrigation System

With extreme weather conditions affecting more and more of the country, having effective freeze protection for your irrigation system’s backflow preventers is no longer a nice-to-have. The right solution can provide year-round peace of mind.

Understanding Backflow Freeze Protection

You know the importance of outfitting your irrigation system with a backflow preventer, protecting the water supply from cross-connection and contamination. When backflow is detected, the device closes off, preventing contamination.

Predictably, freezing conditions can compromise backflow preventers’ ability to function properly. If a device freezes open, it is rendered useless against backflow and cross-connection. This can damage the device and pipes, not to mention the potential risk of water supply contamination.

With freeze events happening with more regularity and severity in historically warmer climates throughout the southern United States, having adequate protection for your waterworks – pumps, wells and irrigation systems and backflow preventers – is a must. Risking your equipment and harming the most sensitive natural resource we have are chances not worth taking.

Types of Backflow Preventers and Vulnerability to Freezing

There are three main varieties of backflow preventers used for irrigation: pressure vacuum breakers, double-check valve and reduced pressure zone valve assemblies.

Pressure Vacuum Breakers (PVBs)

Pressure vacuum breakers feature a smaller footprint and are typically found in residential irrigation used for sprinkler systems or large gardens or greenhouses. As a result, these devices typically aren’t as rugged as double-check or reduced pressure zone valves. 

They are susceptible to failure two different ways: first, they must be installed at the highest point, above the tallest sprinkler head, or they will not function as intended. Second, freeze-related failure will damage the PVB, either with water still in the line, causing it to break, or if properly winterized and exposed to freezing conditions, damaging the bonnet or breaker assembly.  

Double-Check Valve (DCV)

The double-check valve was introduced in the 1950s primarily for use in the fire industry. The idea at the time was novel: in the case of disproportionate water pressure on the property side creating conditions for potential backflow, redundant check valves would trigger to prevent cross-connection from taking place.

As the DC valve grew in use over time, its flaws became more apparent: there was no way to examine the valves for failure; the DC is a closed system. Secondly and related to the first, there was no way to tell if those valves had failed without a professional inspection and a backflow test kit.

The DC valve remains a prominent option today, though in most cases, it is recommended for use only in low hazard situations. 

Reduced Pressure Zone (RPZ) Assemblies

The design flaws in the DC valve prompted the innovation of the reduced pressure zone valve. The RPZ solved for both problems DC valves presented: the fundamental principle was the same, but the RPZ includes a relief valve between the two checks. 

When triggered, both check valves close and the relief valve opens, dumping excess water from the line. While the RPZ solved for the DC’s problem, it created another: if the first check valve fails, the relief valve will continue to dump water until the line is shut off. Because of this, RPZs should exclusively be installed outside and where excess water can flow away from a building. They are considered a high hazard solution.

Both DCs and RPZs are made of metal and are especially susceptible to freezing and failure. They should be properly winterized and protected from the elements in an enclosure that allows for inspection, servicing and proper drainage.

The Importance of ASSE 1060-Conforming Enclosures

The American Society of Sanitary Engineering (ASSE) established uniform guidelines in 1996 covering enclosures for “fluid conveying components” and their strength, drainage capability and ability to withstand cold conditions. 

This is known as the ASSE 1060 standard, and not all enclosures meet ASSE’s standards.

Proper Winterization Techniques for Backflow Devices

Irrigation systems and backflow devices that are not enclosed should be thoroughly winterized. Here are basic steps from our post on winterizing backflows:

• Turn off main water to backflow preventer
• Open sillcock valves and drain all water from line
• Connect a high-volume air compressor
• Turn on faucets, or activate each irrigation system zone, until only air comes out
• Turn valves on either side of backflow to 45 degree angle
• Stop air compressor and disconnect from system
• Remove backflow and store 
• Apply petroleum jelly to union seals and wrap seals with plastic

Regional Considerations for Backflow Freeze Protection

What is needed for backflow protection in New England may not be what’s needed for Texas, which may not be what’s needed in Nebraska, and so forth.

Regardless of where you are, though, if recent winters are any indication, every backflow preventer should be protected from freezing conditions and failure. The risk of damage and water waste or contamination simply isn’t worth it.

A Safe-T-Cover modular aluminum enclosure provides access to your backflow preventer for inspection and maintenance, and its ASSE 1060 Class I rating (with slab-mounted heater) assures you that it will withstand just about any icy punch Old Man Winter throws at it. In addition, with available ventilation, fans and louvers, the same protection works under the summer sun, as well. 

Why worry about detaching and reinstalling equipment when you can install a Safe-T-Cover enclosure and save time every spring and fall?