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 reversal of the flow of water from its intended direction. Backflow is dangerous because it can allow drinking water in plumbing systems to become contaminated and unusable. There are two types of backflow:

  1. Backsiphonage: When a drop in Loudoun Water’s system pressure creates a suction effect drawing water out of a building, house, or other private plumbing system back into the potable water system. (ex. water main break, hydrant flushing.)
  2. Backpressure: When a building, house, or other private plumbing systems with greater pressure than Loudoun Water’s system pressure forces water from the building, house, or private plumbing system back into the potable water system. (ex. pressurized system with booster pumps, chemical feed pumps, boilers, elevated storage tanks, or recirculating systems.)

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?
An approved backflow prevention device is required at the service point of entry 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 if a 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.

Types of properties that are considered high hazard, and are required to install an approved reduced pressure zone (RPZ) backflow prevention device with the addition of an air gap in qualifying applications:

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

What is an “approved” backflow prevention device?
A physical means (air gap) or mechanical device that has been tested and approved by the American Society of Sanitary Engineering (ASSE).

What is an “approved” air gap?
An air gap is a physical separation between a vessel and the supply pipe and shall be at least 8 inches or twice the influent pipe diameter, whichever is greater. Physical separation must be measured vertically from the lowest end of the potable water outlet to the flood rim of the receiving fixture or vessel into which the potable water discharges. Inlet piping shall be mounted external to the vessel and cannot be installed internally for any reason. Air gaps must be physically visible for annual inspection by Loudoun Water, and can be wrapped with #24 stainless steel mesh to prevent exterior contaminants from entering the tank.

Does a storage tank that is supplied by and contains potable water, require an air gap?
Whenever Loudoun Water’s potable water is to be stored in a basin, tank, or reservoir of any kind, an approved Loudoun Water air gap must be provided between the potable supply and the storage vessel.

If my facility has more than one source of water, is an air gap required between the potable and secondary sources?
Whenever a building’s plumbing or industrial process piping is supplied with potable water from Loudoun Water, and also incorporates an auxiliary/redundant source (ex. Ground/Well water, rainwater, storage tank, reclaimed water, process, or industrial water etc.) an approved Loudoun Water air gap shall be provided between the building’s potable service line and the subject plumbing or process piping.

How often must a backflow prevention assembly be tested? 
Backflow prevention assemblies must be tested when first installed and annually thereafter. The test must be performed by a certified tester, all test sheets must then be submitted to Loudoun Water. If a device is removed and reinstalled for any reason, that device is required to be retested following reinstallation/relocation (ex. Irrigation device removal for winterization and reinstallation of that same device the following year.)

Who is responsible for arranging for a testing of a backflow prevention assembly?
Owners are responsible for arranging testing of a backflow prevention assembly. (With new structures, this is typically the contractor)

Who maintains my backflow prevention assembly(ies)?
Owners are responsible for maintaining devices during annual testing or between testing events. The device should always be operational to avoid cross-connection contamination of the internal plumbing and/or the water service from the Loudoun Water main. 

What if my backflow prevention assembly fails the test? 
A notice will be sent to the owner 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 or replaced, then retested by a certified tester at the expense of the customer within 30 days of notification by Loudoun Water.

What happens if I don’t have my assembly tested? 
The annual testing of a backflow assembly confirms from a certified professional that the device is operating properly. The risk of contamination potentially impacts the health of the people in your household as well as other Loudoun Water customers. Owners who do not have properly operating and maintained backflow prevention assemblies will be in non-compliance. Loudoun Water may disconnect and discontinue the water service to any customer who poses a risk to the drinking water supply via an unprotected connection. 

Who is responsible for submitting the sheet to Loudoun Water? 
The certified tester must complete the test form or online webform. If filling out a paper test sheet, the certified tester must provide the test results to the owner and Loudoun Water. Test sheet results can be sent to Loudoun Water by mail at 44771 Loudoun Water Way, Ashburn, VA  20147 or by email to Online webforms are automatically emailed to the owner and Loudoun Water.

What is Loudoun Water’s responsibility to the cross-connection backflow program?
Loudoun Water maintains the backflow test records and Loudoun Water cross-connection backflow inspectors perform inspections of commercial buildings and restaurants annually.

Are there special requirements for Private Booster/Fire Pumps?
Premises having booster pumps or fire pumps connected to the waterworks shall have the pumps equipped with a pressure sensing device to shut off or regulate the flow to prevent a reduction of pump suction line pressure from the potable water system to less than 20 psi gauge. 


Questions/Concerns? Contact Us
Loudoun Water
Cross-Connection Control & Backflow Prevention Department