When Your Reduced Pressure Zone Assembly Fails: Understanding the Consequences and Solutions


Reduced Pressure Zone Assemblies play a crucial role in maintaining the safety of the public water supply.  These devices are some of the most sophisticated out of all the backflow preventers and are designed to prevent the backflow of contaminated water from leaching into the clean water supply.  However, like any mechanical component, RPZ valves can fail leaving you and your facility unprotected.  In this blog, we will explore the consequences of RPZ assembly failures and discuss potential solutions to protect you and the water supply.

Understanding RPZ Assemblies

Reduced Pressure Zone or RPZ assemblies offer the highest level of protection out of all of backflow preventers out on the market.  They are typically used in commercial or industrial settings, and they can even find their way into certain residential settings.  They work by creating a barrier between the potable water and the non-potable water with 2 independent check valves and a relief valve between the two checks.  RPZ’s offer protection against backpressure as well as back siphonage, when the device is in a backflow condition the second check valve closes tight to prevent any non-potable water from entering the potable water supply.  In a back siphonage situation, assuming both check valves holding tight, the relief valve will open dumping all the water out of the device while simultaneously allowing atmospheric air in to create an airgap eliminating the cross connection.  For more on Cross Connections check out our post on this topic.

Common Causes of RPZ Failures
  • Dirt and Debris: Accumulation of dirt, sediment, or other debris can obstruct the internal components of the internal check valves and relief valve, preventing then from functioning properly
  • Corrosion: Over time, corrosion can weaken the materials of the internals of the RPZ, leading it to leak and no longer seal properly causing a complete failure.
  • Improper Installation: If the RPZ is not installed correctly, it may not function properly leaving the water supply vulnerable to contamination.  It is important to note that RPZ’s cannot be installed vertically and/or in pits.  They also must be installed with an air gap of at least one inch and be installed in a room with proper drainage in case the relief port opens and floods the room.
  • Lack of Maintenance: Just like any other mechanical device, RPZ’s require regular testing as well as certain cleaning precautions to ensure the functionality of the device.  Neglecting these tasks will result in the device failing over time.
Consequences of RPZ assembly failures

When an RPZ assembly fails, it can have serious consequences for both public health and the water supply system:

  • Health Risks: The main purpose for these backflow preventers is to protect the public from exposure of contaminated water.  A failure of any kind can lead to pollutants or chemicals backflowing into the clean water supply, posing health risks to consumers.
  • Legal and Regulatory Issues: RPZ assemblies are often required by local plumbing codes and regulations.  A failure to maintain or replace a malfunctioning unit can result in significant fines as well as other legal consequences.
  • Contaminated Water Supply: In the event of a RPZ failure, the water supply may need to be shut down until the issue is resolved, causing disruptions and inconveniences for consumers.
Solutions for RPZ Assembly Failures

It is crucial to stay on top of routine maintenance of your RPZ assembly.  Here are some steps to consider:

  • Professional Backflow Testing: Licensed and insured professionals conduct quarterly/bi-annual/annual backflow testing to ensure that the device is meeting requirements.
  • Cleanouts: When a part of the device fails for whatever reason, it is important for a licensed technician to take the device apart and clean all of the check valve mating surfaces to ensure that there is no debris preventing the closure of the check valves.  If this fails to work further repairs are required.
  • Immediate Repairs: Sometimes cleanouts will not solve the problem, when a check valve becomes damaged for whatever reason it is important to replace the internal parts with urgency to help mitigate the risk of a backflow occurrence.
  • Record Keeping: It is important to keep track of any testing, service or repairs that have been made on the assembly.  This is the only way to demonstrate compliance with regulatory requirements.

Reduced Pressure Zone Assemblies are essential components of the water supply system, service to protect public health by preventing backflow contamination.  When these assemblies fail, the consequences are severe, including health risks and legal issues.  Regular inspections, maintenance, and professional testing are essential to prevent RPZ failures.  By staying proactive and vigilant, we can maintain the integrity of our water systems and protect the health and well-being of communities.

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