Understanding Backflow Prevention Devices
Backflow preventers come in several types, each designed for specific hazard levels and installation scenarios. The type of device required on your property depends on the degree of hazard posed by the cross-connection — meaning how dangerous the potential contaminant could be if it entered the public water supply.
As a TCEQ licensed backflow tester, Atlas Backflow of Texas tests and repairs all types of backflow prevention assemblies. Here is a complete guide to the devices you may encounter on your DFW property.
Reduced Pressure Zone Assembly (RPZ)
The RPZ is the highest level of backflow protection available. It contains two independently operating check valves separated by a pressure-monitored relief valve. If either check valve fails, the relief valve opens and discharges water to the atmosphere rather than allowing contamination to pass through.
Where RPZ devices are required:
- Commercial and industrial properties with chemical storage
- Medical and dental facilities
- Car washes and laundromats
- Properties with auxiliary water supplies (wells, reclaimed water)
- Any connection classified as a "high hazard" cross-connection
Key characteristics:
- Must be installed above ground (12 inches minimum above grade in most DFW jurisdictions)
- Will discharge water from the relief valve during normal operation if a check valve fails
- Requires annual testing by a TCEQ licensed backflow tester
- Most expensive to install and maintain, but provides the highest protection
Double Check Valve Assembly (DCVA)
The DCVA contains two independently operating check valves in series. It provides protection against both backpressure and backsiphonage but does not have a relief valve, so it cannot discharge to atmosphere if a check valve fails.
Where DCVA devices are required:
- Fire suppression systems (wet systems without chemical additives)
- Commercial properties with moderate hazard cross-connections
- Some residential applications where local code permits
Key characteristics:
- Can be installed below ground in a vault
- Does not discharge water, making it suitable for indoor installation
- Requires annual testing by a certified backflow tester
- Less expensive than RPZ but provides a lower level of protection
Pressure Vacuum Breaker (PVB)
The PVB is the most common backflow preventer found on residential irrigation systems in the DFW area. It contains a single check valve and an air inlet that opens when pressure drops, breaking the siphon effect.
Where PVB devices are required:
- Residential irrigation systems
- Some commercial landscape irrigation
- Connections where only backsiphonage protection is needed
Key characteristics:
- Must be installed above the highest sprinkler head (at least 12 inches above)
- Only protects against backsiphonage, not backpressure
- Most affordable backflow preventer option
- Requires annual testing by a TCEQ licensed backflow tester
Atmospheric Vacuum Breaker (AVB)
The AVB is the simplest type of backflow preventer. It uses a single float check that opens an air vent when water flow stops. AVBs are not testable assemblies and are only suitable for very low-risk applications.
Key characteristics:
- Cannot be installed with any downstream shutoff valves
- Not suitable for continuous pressure applications
- Does not require annual testing (not a testable assembly)
- Limited to non-health-hazard applications
Which Device Does Your Property Need?
The type of backflow preventer required for your property is determined by your local water utility's cross-connection control program. When a new connection is established or an existing one is evaluated, the utility assigns a hazard classification that dictates the minimum level of protection required.
If you are unsure what type of device is installed on your property or whether it meets current requirements, Atlas Backflow of Texas can perform a free evaluation. We will identify your device, verify it is appropriate for your application, and schedule your annual backflow test.
Call (817) 612-6088 or email [email protected] for a free consultation.
