Cross Connections & Backflow Prevention

Thornton has implemented an operational backflow and cross-connection control program. A cross-connection control program is critical because controlling cross-connections and preventing backflow is critical to ensuring the safety of the drinking water we provide to our residents.

It’s up to us to ensure that all backflow prevention assemblies within the water distribution system are tested and maintained annually.

  • Facility Owners: See Important Information below for testing and inspection information.
  • Annual Inspections: Submit an annual report or create an account with Backflow Solutions Inc.

What is a Cross Connection?

Two sinks with one filled with water and the faucet in the water and a sink on the right with the faucet above water

A cross-connection is a direct arrangement of a piping line that connects the potable water supply to a line containing a contaminant. An example is the standard garden hose attached to a sill cock, with the end of the hose lying in a cesspool. Other examples are a garden hose attached to a service sink with the end of the hose submerged in a tub full of detergent, supply lines connected to bottom-fed tanks, and supply lines connected to boilers.

What is Backflow?

Backflow is the unwanted flow of water in the reverse direction. There are two types of backflow: back pressure and back siphonage. Back pressure occurs when elevation or a mechanical pump causes the system pressure to be greater than the supply pressure. Back siphonage occurs when there is a loss in supply pressure. A backflow system is installed to prevent any contamination of the drinking water supply and maintain water quality.

Back Siphonage is reverse flow due to supply pressure loss and back pressure caused by pump greater than system pressure

Annual Inspections

The city looks for potential risks to the water distribution system via annual inspection of all properties —commercial, industrial, and non-single-family residences (any residence greater than 2 units). If the plumbing system inside your building were built to code, these risks would be well-managed. However, older buildings may need to be brought up to current plumbing requirements.

Additionally, all commercial, industrial, and non-single-family residences (any residence greater than two units) must have approved backflow devices installed and tested annually to comply with the city’s Cross-Connection Control & Backflow Prevention Program.

Thornton City Ordinance 74-156 requires backflow preventers or cross-connection devices. A certified Backflow Technician must conduct operational tests on all necessary backflow prevention assemblies at installation and at least annually after that. Test results must be submitted online at Backflow Solutions, Inc., before the annual test due date.

Testing Companies

Many backflow testing companies serve Thornton. The city of Thornton does not recommend any testing company over another. Please contact us for further information regarding the testing process or requirements.