If you’ve worked with RPZ backflow preventers long enough, you’ve probably heard someone say, “We don’t really need RPZ freeze protection in this region.” Maybe you’ve even said it yourself.
But even in warmer climates, unexpected freezing temperatures are more common and more costly. Whether you’re in the Sun Belt or the Midwest, freeze protection for RPZ assemblies isn’t optional anymore. It’s risk mitigation.
Most jurisdictions still rely on vaults, cages or mechanical room installs for backflow assemblies. These options may check the box for installation, but they fall short where it matters most: protection.
That’s especially true for RPZ assemblies, which are designed to discharge water in the event of failure or debris interference. When that discharge happens in cold conditions, things get icy fast. Here’s what every engineer, facility planner and water authority should know about how to properly protect RPZs when the temperature drops so you don't end up with costly repairs.
Reduced Pressure Zone (RPZ) backflow preventers are designed for high-hazard applications. If anything goes wrong — if one of the check valves fails or if debris interferes with sealing — the relief valve opens and dumps water out of the assembly. It’s a critical feature that protects the public water supply from contamination. But that same feature also makes RPZs especially vulnerable to freeze damage.
During a freeze, any standing water in or around the relief valve will expand, leading to cracks, broken components or a full assembly failure. That’s true whether the RPZ is in a cage, vault or sitting just a few feet inside a building. And when an RPZ fails, the water it was supposed to protect flows in the wrong direction.
Still think freeze protection doesn’t apply to your area?
These aren’t fringe cases. They’re proof that unexpected cold snaps can happen anywhere. And they don’t need to last long to cause serious damage.
Many jurisdictions still specify backflow cages and some even attempt to winterize them with insulated blankets. While it may seem like a quick fix, these approaches don’t solve the core issue: they don’t provide reliable freeze protection or proper drainage.
A cage doesn’t prevent freezing, but it does make your equipment visible to vandals and exposed to the elements. Blankets or bags may trap some heat temporarily, but they weren’t designed for the dynamic needs of an RPZ and certainly don’t meet any standard for performance or safety.
Vaults are even worse. They’re confined spaces, expensive to maintain and they flood, creating a direct cross-connection risk if submerged valves are compromised. OSHA classifies vaults as confined spaces and anyone entering them must follow strict safety protocols. That’s a lot of cost and liability for something that doesn’t actually prevent freezing.
The American Society of Sanitary Engineering developed the ASSE 1060 standard specifically to address these risks. ASSE 1060 enclosures are engineered to protect backflow preventers from freezing, vandalism, flooding and physical damage.
For RPZ assemblies in cold climates — or anywhere a freeze event is even remotely possible — you need a Class 1 enclosure. These units are built to maintain an internal temperature of at least 40°F even when the external temperature drops to -30°F. They include built-in heaters, sufficient insulation (R-value of 8 or more) and a drainage system designed to handle RPZ relief valve discharge.
But ASSE 1060 isn’t just about heat. It also requires adequate testing access, secure locking mechanisms and structural integrity that meets or exceeds a 100 psf vertical load. It’s the industry benchmark for a reason, and it’s increasingly being adopted as a requirement by jurisdictions updating their standards.
Protecting an RPZ properly starts with choosing the right enclosure, but design execution matters, too. Here are a few things to consider when planning your next install:
If you’re using RPZs in your system — and you probably are if you’re protecting high-hazard cross-connections — then freeze protection isn’t a maybe. It’s a must.
With changing weather patterns, aging infrastructure and growing liability exposure, it’s time to move past cages and vaults. A heated, insulated aluminum enclosure built to ASSE 1060 standards will keep your water system safe, compliant and operational for decades.
Get a deeper look at what works — and what doesn’t — when it comes to protecting RPZ assemblies. Download the Best Practices in Backflow Protection Guide. It covers: