Cross Connection / Backflow

Protect your drinking water from cross-contamination

Public drinking water systems may become polluted or contaminated through uncontrolled cross-connections. A cross-connection is an actual or potential connection between the public water system and any other system that could accidentally introduce a contaminant into the public water system. This is known as a backflow event. Water normally flows in one direction, from the public water system through the customer’s plumbing to a sink tap or other plumbing fixture. Under certain conditions, backflow can occur.

Backflow could be caused by a backsiphonage, or a backpressure condition. Backsiphonage is due to a loss of pressure in the public water system during a high withdrawal of water for fire protection, a water main or plumbing system break, or a shutdown of a water main or plumbing system for repair. Backpressure is due to any condition in the customer’s system that would increase their system pressure above the public water supply pressure, causing a reversal of flow.

Residential irrigation, and fire suppression systems, require a mechanical backflow prevention device. The pressure vacuum breaker (PDF) or reduced pressure assembly (PDF) are two examples of the most common backflow prevention assemblies used in homes. Care should be taken to prevent an uncontrolled cross connection in your home. 

How to prevent an uncontrolled cross connection

  1. Learn about backflow prevention (PDF).
  2. Do not submerge hoses - especially when filling pools, spas, ponds or other areas that have a circulation pump. 
  3. Do not use a hose to unplug blocked toilets, sewers, etc.
  4. If hose bibbs are not equipped with a built-in vacuum breaker from the manufacturer, install a hose connection vacuum breakers fitting on all hose-bibbs, and threaded faucets around your home. This is especially important when using spray attachments for spraying herbicides and pesticides.
  5. Install an approved backflow prevention assembly on all underground lawn irrigation systems. (This is a Town of Castle Rock requirement).
  6. Ensure proper winterization of the irrigation system to help prevent freezing and breaking of the backflow prevention assembly.
  7. Do not “blowout” the irrigation system with compressed air through the approved backflow prevention assembly, as this could compromise its capability. Rather, install a blowout connection immediately downstream of the backflow device to blowout the system. 
  8. Do not connect waste pipes from water softeners or other in-home water treatment systems to the sewer, submerged drain pipe, etc.
  9. Annually inspect/test backflow prevention devices (recommended for irrigation systems, required for fire suppression systems). Find certified Cross Connection / Backflow Prevention Testers (PDF) registered with the Town.
meter stack installation

Cross Connection Backflow Certification

Only certified backflow assembly testers are permitted to test backflow assemblies within the Town of Castle Rock. Existing and prospective testers must submit a copy of the current tester certification and gauge calibration(s), as well as certificate(s) of insurance.

Certification / education classes will be held anytime there are updates to the Town’s Municipal Code regarding cross connections / backflow or the Town’s Cross Connection Manual. 

A current list of certified Backflow Prevention Testers (PDF) can be viewed online.

Questions: Email us or call us at 720-733-6000.