Backflow Rules

Backflow is the reverse flow of water into the water supply, which typically occurs if there is an unexpected decrease in water pressure, such as a break in the water main.

While the condition has the potential to be dangerous, measures can be taken to protect against contamination of the public supply of tap water.

All commercial properties served by the Westbury Water District are required to have an RPZ backflow device in place.

Westbury Water residential consumers who have an underground irrigation system, swimming pool or any other direct connection to Long Island’s public drinking water supply, are required to install a backflow device to their service line. Also referred to as a double-check valve, a backflow mechanism prohibits any seemingly harmful substance from contaminating Long Island’s public drinking water supply.

Should a Westbury Water consumer leave a hose in the swimming pool during this moment, the device will prevent chlorinated water from flowing backwards into the hose and contaminating the water source.

Testing of the backflow prevention device must be performed by a state certified tester upon installation, and annual testing must be conducted thereafter. Each year a certified tester must test the device and file the results with the Westbury Water District and the Nassau County Department of Health. The form used must be completed in its entirety, otherwise it will be rejected.

Click here to download New York State Department of Health Testing Form

Click here to download list of Nassau County Certified Backflow Testers

Cross Connection


Section 1. Authority

Pursuant to the authority vested in the Board of Commissioners of the Westbury Water District, the Superintendent of the Westbury Water District, or his designated agent, shall inspect the plumbing in every premises in the District, at prescribed intervals, between the hours of 9:00 a.m. and 4:00 p.m., to ensure that the plumbing system was installed and is maintained in such a manner as to safeguard the potable water supply by preventing backflow into the potable water supply system.

Inspection – The Superintendent, or his designated agent, shall have the right of entry into any property or building in the Westbury Water District for the purpose of making an inspection of the plumbing system.

Statutory Authority – Public Health Law 225, New York State Sanitary Code, Part 5, Drinking Water Supplies, 5-1.31, Cross Connection control – (a) Except when the supplier of water determines that no significant hazard is posed by the premises served, the supplier of water shall protect the public water system from existing or potential contamination by containing within or limiting the existing or potential contamination to the premises of the user in the following manner:

  • by requiring an acceptable air gap, reduced pressure zone device, double check valve assembly or equivalent protective device, acceptable to the Commissioner, consistent with the degree of hazard posed by the premises served by the connection.
  • by requiring the users of such connections to submit plans for the installation of protective devices to the supplier of water and the State for approval.
  • by assuring that all protective devices be inspected and tested at least annually by the supplier of water or by the user. The records of such inspections and tests shall be made available to and maintained by the supplier of water.