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Backflow Prevention Devices Fact Sheet


Water for the University of Maryland is supplied and delivered through piping systems provided by the Washington Suburban Sanitary Commission (WSSC). This water is used for drinking (potable water) and for industrial and commercial facilities such as laboratories, laundries, hospitals, etc. Cross-connections between potable water distribution systems and industrial/commercial piping systems could create a potential for backflow of contaminated wastewater into the drinking water system if there is a loss of water pressure as may occur during a pipe break or during plumbing maintenance. For this reason, backflow prevention devices such as check valves, air separation gaps and similar devices are installed in certain situations to prevent cross-contamination of the drinking water supply. These backflow prevention devices are required by code and must be installed and periodically tested by qualified personnel. Different devices are required for different types of facilities and uses. High hazard areas such as laboratories, clinics and hospitals require sophisticated backflow prevention devices.

There are many backflow prevention devices installed in University of Maryland facilities. Backflow prevention devices must often be installed during new construction or renovation/repair of existing facilities. This Fact Sheet describes the requirements for installation, testing, registration and repair of backflow prevention devices.


Backflow means the flow of water or other liquids, mixtures or substances into the distribution pipes of a potable water supply system. Backflow may occur when non-potable water is siphoned into the pipe distribution system as a result of loss of pressure.

Backflow Prevention Device means a method approved by the WSSC for the prevention of backflow.

Certified Backflow Prevention Mechanic means a person who has demonstrated competency in inspection and testing of backflow prevention devices.

Cross-connection is a connection between a distribution pipe of potable water and any waste pipe, drain, sewer, non-potable system or other unapproved source.

Applicable Regulation

  • Plumbing and Gas fitting Regulations of the Washington Suburban and Sanitary Commission.
  • 2000 ICC International (B.O.C.A. National) Mechanical Code.

Summary of Requirements

  • Backflow prevention devices must conform with the American Society of Safety Engineers (ASSE) standards as listed in WSSC regulations.
  • Backflow prevention devices shall be selected from the approved list as indicated in Table 4.5 of the WSSC Code.
  • Backflow prevention devices must be installed inside buildings in areas capable of maintaining a minimum temperature of fifty degrees Fahrenheit, except those approved for seasonal removal and replacement.
  • Backflow prevention devices must be readily accessible for inspection, testing and maintenance.
  • Backflow prevention devices must not be installed in pits or similar submerged areas.
  • Backflow prevention devices shall be inspected and tested after initial installation.
  • Routine inspection, testing and overhaul of backflow prevention devices is the responsibility of the property owner, and shall be conducted at frequencies specified in the WSSC Code.


  • Personnel who perform backflow prevention inspection, testing and overhaul must be certified (32 hour training class) as a Backflow Prevention Mechanic by the Maryland Plumbing, Heating and Air Conditioning Contractor's Association.
  • Personnel who install backflow prevention devices must meet the requirements for designation as Master Plumbers.


  • Backflow prevention devices must be registered with WSSC.
  • Inspection and testing of backflow prevention devices must be documented to WSSC on provided forms.


The facility owner is responsible for ensuring that backflow prevention devices are inspected, tested and overhauled by a Certified Backflow Prevention Mechanic per the frequency as specified in the WSSC Code.


Records detailing the installation, inspection, testing and overhaul of backflow prevention devices must be maintained by the facility owner and forwarded to WSSC.

University Resources

Department of Environmental Safety, Sustainability and Risk (301) 405-3960
Office of Facilities Management Piped Services Shop (301) 405-3277
ESSR Fax No.    (301) 314-9294
ESSR Website:

Written 5/98
Revised 4/05