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 annually by a certified tester to make sure it is adequately working.

Backflow prevention protects both the customer’s drinking water pipes in their home 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 home 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.  Common types of cross connections in homes include:

  • Underground sprinkler systems: Dirty water from the lawn can be siphoned back into the sprinkler head and flow back into the house water supply. It is required by Federal and State regulations that this device be tested when installed and annually by a certified tester to ensure it is working properly.
  • Garden hoses and hose bibs: If an insecticide or herbicide dispenser is attached to a garden hose, a pressure drop can cause chemical-laden water to be pulled from the hose and into the house water supply. 
  • Swimming pool or hot tub: If filled with a hose submerged in the water, pool water can be drawn back into the hose and into a house’s water supply.

How does backflow occur?
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. Easy ways to prevent backflow are to:

  • Avoid submerging a garden hose into a bucket, pool, spa, tub or sink.
  • Always keep the end of a hose away from possible contaminants.
  • Always have a backflow prevention device on your garden hose when putting on a spray or cleaning attachment.

What are my responsibilities as a backflow prevention assembly owner?
Owners must have their backflow prevention device tested annually as a way to protect the public water supply from possible contamination. Failure, refusal or inability on the part of the consumer to install, have tested and maintain required backflow prevention assemblies within 15 days of notification by Loudoun Water shall constitute a violation.

How often must a backflow prevention assembly be tested?
Backflow prevention assemblies must be tested when first installed and 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 Water, Ashburn VA 20147 or by email to or by fax at 703-729-9494

What if I didn’t use my irrigation system this year?
Unless your system has been cut and capped by a certified irrigation contractor or plumber, owners must have their backflow prevention device inspected annually.