The Loudoun Water Cross-Connection Backflow Program is responsible for protecting the water distribution system from potential hazards caused by cross-connections of non-potable water systems.  Loudoun Water is committed to  ensuring tap water is safe to drink, which according to Federal and State regulations, requires backflow preventers be tested when first installed and annually by a certified tester to make sure it is adequately working.

Backflow prevention protects both the customer’s drinking water pipes in their business as well as the water mains in the streets. Otherwise, if a drop in pressure occurs, any connection to a non-potable source could be siphoned back into the customer’s business or Loudoun Water’s service line, which is dangerous.  The only way to prevent such incidents from occurring and to maintain safe drinking water is to use a backflow prevention device that is correctly installed and maintained properly.

What is a cross-connection?
A cross-connection is  a temporary or permanent connection between a potable (drinking) water supply and a non-potable source. 

What is backflow?
Backflow is the undesirable flow of non-potable water or other substance through a cross-connection back into the consumer’s plumbing system or public water system due to backpressure and backsiphonage.

How does backflow occur?
Backflow can occur when a premises’ water pressure is higher than the pressure in the water distribution system.

What is backpressure?
Backpressure is caused by a downstream pressure that is greater than the supply pressure of the public water system or the consumer’s water system. This is caused by elevated plumbing, booster pumps, pressure vessels, etc.

What is backsiphonage?
Backsiphonage is backflow caused by negative pressure in the public water system or the consumer water system. This can potentially occur during a water main break.

Why should I be concerned?
There can be many hazards present in a water distribution system which can be categorized as either high or low.

  • High hazards – any substance that if introduced to the public water system could cause serious illness, death or could spread diseases. For example, industrial fluids or waste.
  • Low hazards – any substance that if introduced to the public water system would not be a health hazard but would constitute a nuisance or be aesthetically objectionable.

Do the requirements apply to me?
A backflow prevention device shall be installed at each service connection to a consumer’s water system serving premises where the following conditions exist:

  1. Premises on which any substance is handled in such a manner as to create an actual or potential hazard to a waterworks (this shall include premises having sources or systems containing process fluids or waters originating from a water system which are no longer under the control of the water provider).
  2. Premises having internal cross connections that, in the judgment of the water provider, may not be easily correctable or intricate plumbing arrangements which make it impractical to determine whether or not cross connections exist.
  3. Premises where, because of security requirements or other prohibitions or restrictions, it is impossible or impractical to make a complete cross connection survey.
  4. Premises having a repeated history of cross connections being established or reestablished.
  5. Premises having fire protection systems utilizing combinations of sprinklers, fire loops, storage tanks, pumps, antifreeze protection, or auxiliary water sources including siamese connections.
  6. Other premises specified by the water provider when cause can be shown that a potential cross connection hazard not enumerated above exist.

What types of properties are required to install a backflow prevention device?

  • Hospitals, mortuaries, clinics, veterinary establishments, nursing homes, and medical buildings;
  • Laboratories
  • Piers, docks, and waterfront facilities
  • Sewage treatment plants, sewage pumping stations or storm water pumping stations
  • Food and beverage processing plants
  • Chemical plants, dyeing plants, and pharmaceutical plants
  • Metal plating industries
  • Petroleum or natural gas processing or storage plants
  • Radioactive materials processing plants or nuclear reactors
  • Car washes and laundries
  • Lawn sprinkler systems, and irrigation systems
  • Fire service systems
  • Poultry processing plants
  • Farms where the water is used for other than household purposes
  • Commercial greenhouses and nurseries
  • Health clubs with swimming pools, therapeutic baths, hot tubs or saunas
  • Paper and paper products plants and printing plants
  • Pesticide or exterminating companies and their vehicles with storage or mixing tanks
  • Schools or colleges with laboratory facilities
  • Multiuse commercial, office, or warehouse facilities
  • Any facility with reclaimed water
  • Others specified by the provider or the division when reasonable cause can be shown for a potential backflow or cross connection hazard

How often must a backflow prevention assembly be tested?
Backflow prevention assemblies must be tested when first installed and annually.

How often does Loudoun Water inspect for compliance of your backflow devices?
Loudoun Water cross-connection backflow inspectors perform inspections of commercial buildings and restaurants annually.

Who is responsible for arranging for a testing of a backflow prevention assembly?
Owners are responsible for arranging for the testing of a backflow prevention assembly. 

Who is responsible for sending in the completed test sheet?
The owner is responsible for sending the completed test sheet to Loudoun Water by mail at 44771 Loudoun Water Way, Ashburn VA 20147 or by email to or by fax at 703-729-9494

What if my backflow prevention assembly fails the test?
A notice will be sent to the owner and tenant of any building or structure that is found to have devices in violation of the Loudoun Water Cross-Connection Backflow Program. Devices found to be in non-compliance shall be repaired, overhauled or replaced by the customer at the customer’s expense within 15 days of notification by Loudoun Water.

What happens if I don’t have my assembly tested?
Owners who do not have backflow prevention assemblies tested will be found in non-compliance. Loudoun Water may disconnect the water service to any customer posing a risk to the drinking water via an unprotected connection due to the risk of a contamination event at your business affecting other Loudoun Water customers.