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The Town of Silverthorne Water Department's main goal is to provide the highest quality of water possible. If properties have potential water contaminants it poses a risk to everyone. The Town is mandated by the State of Colorado and the United Stated Environmental Protection Agency (EPA) to identify and protect all connections to the Towns water system. This protection comes in the form of a backflow prevention device.

  • What is backflow? “Backflow (BF) is the undesirable reversal of the flow of water or mixtures of water and other undesirable substances from any source (such as used water, industrial fluids, gasses, or any substance other than the intended potable water) into the distribution pipes of the potable water system.”
    • Layman’s terms – It’s a reversal from the normal flow of water due to: an internal increase in pressure, a loss of pressure in the watermain due to fire flow conditions or high demand, or a temperature difference like a hot water heater or boiler system, which results in pressurizing the customer's water system. 
  • What is a backflow prevention device? A backflow device is a check valve system that prevents water from traveling in the reverse direction to the Town water supply. These devices must be approved by the State of Colorado. 
  • What is a cross connection? A cross connection is a potential connection from a non-potable water source to the Towns drinking water system. Irrigation systems, fire suppression systems, industrial chemicals, etc.
  • Do I have one? Every single family residence should have at least a non-testable dual check backflow device. (See Photo 1 below) You must have a testable reduced pressure backflow device (RP) if you have a fire suppression system, irrigation system, chemical processing, pressure pump connected to the Town water system. All commercial establishments must have an RP.  
  • Who can test the device? A currently certified American Backflow Prevention Association (ABPA) or American Society of Sanitary Engineering (ASSE) backflow professional. Here is a complete list of all certified backflow testers that have tested in the Town - Certified Tester List
  • Survey - The Towns Water Department is required by the EPA and the State of Colorado to complete a site visit to EVERY CONNECTION IN THE SYSTEM* to identify hazards or potential hazards, verify that there is a BF device and to make sure that the testable devices are getting tested annually. There is no “grandfathering in” * The only exceptions to the survey requirement are single family residences without: a fire suppression system, hot tubs with permanent plumbing and water storage tanks that are directly connected to the water system. The TOS Water Department survey is only looking at connections to the water system at the water meter. 
  • For more information on the theory of backflow, common devices, and applications please visit the US EPA Cross Connection Manual website. 

Requirements for Property Owners

  • Every property in the Town of Silverthorne is required to have a backflow device that provides an equal or higher degree of protection than is required by State Law. 
  • Testable backflow devices must be tested annually! It is up to the property owner to have this scheduled and completed. The testing company is required to submit the paperwork to the Town at and the owner is to keep a copy for 3 years.
  • The Town of Silverthorne Water Department is required to discontinue water service to the property if: devices are not tested annually, if the device fails and is not repaired (within 90 days), if there is a hazard that is not protected by a backflow device (120 days after discovered), or if the property owner does not permit a site survey to be completed. 


  • New Construction - All new single family homes are required to have at least a dual check backflow as part of the water meter setup.
  • Existing homes – Some older homes in the Town do not have dual check backflow on their service.
    • Upgrading - The Town understands the challenges that face property owners to upgrade or modify their plumbing systems. The homeowner is responsible for properly installing the device while protecting their system from thermal expansion. See Thermal Expansion Information website for more information. If you would like to upgrade and have questions about our policies and incentives, please contact the Town Water Department for further information. 
  • All irrigation, commercial, and industrial buildings are required at be protected with an approved, testable, Reduced Pressure (RP) backflow prevention device.
  • All single family homes are required to be protected with at least an approved dual check backflow device, though a higher hazard backflow device may be used, i.e. Double Check or a Reduced Pressure (RP).
  • Any home or building with a fire suppression system must have a RP. Some single family homes have water storage tanks and a pump for their fire suppression system. These are allowed as long as they are isolated with an approved air gap (2x pipe, 1” min) or an RP backflow device.

Examples of backflow devices:

Duel Check











Photo 1 Duel Check required on (All residential buildings)

Large RP BF

Photo 2 Reduced Pressure (RP) Large applications (Warehouse/Hotels)

Small RP BF

Photo 3 Reduced Pressure (RP) Small/Medium applications (Residential/Commercial)


Certified Tester Requirements

The Town of Silverthorne requires that all certified backflow technicians are to have: a current certification (ASSE or ABPA), a current calibration report for the gauge used, and if testing a fire system, a valid State of Colorado issued Fire Suppression System Contractor Certification. These documents are required to be submitted to the Town annually at

Test forms are required to include: BF size, manufacture, model, type, serial number, location, type of use, line PSI, date tested, tester certification and expiration date, gauge serial number and expiration date, owner contact information, and ideally a photo of the installation. 



For further information or questions on backflow devices, testing and applications please contact:

Chris Shelden at (970) 513-4870 or