heating system & hot water tanks

Methods to Prevent Backflow and Install Backflow Prevention Devices

Introduction

Backflow occurs when contaminated water flows backward into the clean water supply, posing serious health risks. Preventing backflow is crucial for maintaining safe drinking water. This guide covers methods to prevent backflow and how to install backflow prevention devices.

Understanding Backflow

Backflow can occur in two main ways:

Methods to Prevent Backflow

  1. Air Gap:
    • Description: A physical separation between the water supply outlet and the highest possible water level in a fixture.
    • Application: Common in sinks, bathtubs, and other fixtures.
    • Installation: Ensure a sufficient vertical distance between the supply outlet and the fixture’s flood level rim.
  2. Check Valves:
    • Description: Allow water to flow in one direction only.
    • Types: Single check valves and double check valves.
    • Installation: Installed inline with the water supply; ensure correct orientation according to the flow direction.
  3. Reduced Pressure Zone (RPZ) Valves:
    • Description: Consist of two independent check valves with an intermediate relief valve.
    • Application: Used in high-hazard situations.
    • Installation: Typically installed by professionals due to complexity; follow manufacturer’s guidelines for positioning and orientation.
  4. Pressure Vacuum Breakers (PVB):
    • Description: Prevents back siphonage by allowing air into the system when a vacuum is detected.
    • Application: Used in irrigation systems and other outdoor water uses.
    • Installation: Must be installed above the highest point of downstream piping.
  5. Double Check Valve Assemblies (DCVA):
    • Description: Consist of two check valves assembled in series.
    • Application: Suitable for moderate hazard situations.
    • Installation: Ensure accessibility for maintenance and testing.

Steps to Install Backflow Prevention Devices

  1. Assessment:
    • Determine the level of hazard (low, moderate, or high) to select the appropriate device.
    • Evaluate the plumbing system layout and identify potential backflow points.
  2. Preparation:
    • Gather necessary tools and materials.
    • Shut off the main water supply before installation.
  3. Installation:
    • Air Gap: Simply ensure the outlet is adequately elevated.
    • Check Valves and RPZ Valves:
      • Cut the supply pipe where the device will be installed.
      • Fit the device into the plumbing system using appropriate fittings.
      • Ensure the device is installed in the correct orientation (check manufacturer’s instructions).
    • Pressure Vacuum Breakers:
      • Install above the highest downstream piping.
      • Ensure there are no obstructions that could prevent the device from functioning.
  4. Testing and Maintenance:
    • After installation, turn on the water supply and check for leaks.
    • Test the device according to local regulations (often requires a certified tester).
    • Schedule regular maintenance to ensure the device remains functional.

Conclusion

Preventing backflow is essential for protecting the water supply from contamination. Using methods such as air gaps, check valves, RPZ valves, pressure vacuum breakers, and double check valve assemblies, along with proper installation and maintenance, ensures a safe and reliable water system. Regular inspections and adherence to local codes are key to effective backflow prevention.

Additional Resources

Ensuring proper backflow prevention safeguards public health and maintains the integrity of the water supply system.