Reduced Pressure Zone (RPZ) enclosures are gaining in popularity, but not fast enough. Installing your backflow preventer in an outdoor above-ground enclosure is the safest option. But we still have about 70 percent of the country using double-check valve assemblies that are either in a vault or inside buildings. That’s not good.
Backflow prevention devices are needed on public water systems to keep contaminants from entering the public water system. Without a backflow preventer, back-siphonage or backflow of the water can occur. Backflow preventers have either a double-check valve assembly or an RPZ. (I would take this sentence out, there are many types of backflow preventers, some testable, some non-testable, but double checks and RPZs are not the only types)
They operate by allowing water to flow in only one direction — whether it is into a boiler, a doctor’s office, a dentist’s chair, or into the building itself. Backflow preventers are required wherever an end user poses a risk of polluting the city’s water. RPZs are fail-safe because of its relief valve. If the zone of pressure inside the valve is compromised for any reason, the relief valve opens, and the water is expelled. A double-check valve assembly also protects, but unless you test it daily, there’s no way to know if a problem is imminent. That’s why RPZs provide the highest level of protection when they’re installed outside of the building and above ground.
But for as much protection as an RPZ provides, it must also be protected. In order for your RPZ enclosure to be fully protected, it must comply with the ASSE 1060 standards. So, let’s take a look at the standards and how they ensure your backflow preventer is safe when it’s in a backflow enclosure.
ASSE 1060 Standard 1: Freeze Protection
In order to provide maximum protection, your RPZ enclosure must allow for freeze protection up to minus 30 degrees Fahrenheit. Your enclosure must also be heated to an inside temperature of 40 degrees Fahrenheit when the temperature drops to minus 30 degrees outside.
There are wall-mounted-heaters, with features like a built-in thermostat, that meet ASSE 1060 Class 1 for use as freeze protection. But a slab-mounted heater is your best option. It not only meets all ASSE 1060 requirements, but it provides heat to the equipment inside your enclosure, as well as the riser pipes beneath the slab.
ASSE 1060 Standard 2: Structural Strength
RPZ enclosures must also be designed to meet ASSE 1060’s structural strength requirements. This means it can handle a vertical load of 100 pounds per square foot.
ASSE 1060 Standard 3: Proper Drainage
If there is a backflow event, you will need adequate drainage for RPZ relief conditions. RPZ enclosures are designed with the RPZ in mind. They have the proper drainage to allow discharged water to flow out of the box, are insulated for valve frost protection, and keep thieves away from the device's valuable metal.
ASSE 1060 Standard 4: Access requirements for Testing and Maintenance
Your RPZ enclosure must allow access to your equipment and its components. In fact, components must be within 24 inches of the access opening. These include:
- Test cocks
- Valve handles
- Hand wheels
Your enclosure must also have hinged access panels that can be restrained in the open and closed position. Plus, all unrestrained panels and horizontally-hinged panels must weigh 70 pounds or less.
ASSE 1060 Standard 5: Specified Materials of Construction
Your exposed exterior wall panel materials can consist of materials like aluminum, stainless steel or fiberglass. Your exposed interior wall panels can be made from materials like cedar or other approved external materials — but this must be specified.
ASSE 1060 Standard 6: Security and Vandalism Protection
Your RPZ enclosure should be designed with lockable access panels. Or you can gain access with a keyed device or padlocks.
RPZ Enclosures Provide Maximum Protection
There are really only a few reasons why anyone might want to install a backflow prevention assembly in a pit or a vault. They’re either trying to protect it from the weather, keep it from being vandalized, or for aesthetic reasons. But even the USC Foundation recommends all assemblies be installed above grade. If you’re concerned about safety, there’s only one place to install your RPZ: In an RPZ enclosure that is outside the building.
Ironically, custom enclosures are often less expensive than standard enclosures because they fit your equipment perfectly. You don’t have to overspend on a standard enclosure that is too big. To learn more about what size enclosure you might need, consult our “How To Buy” guide.