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Virginia Administrative Code (Last Updated: January 10, 2017) |
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Title 12. Health |
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Agency 5. Department of Health |
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Chapter 590. Waterworks Regulations |
Section 620. Type of protection required
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The type of protection required shall depend on the degree of hazard which exists or may exist and on the method of potential backflow. Backflow occurs either by back pressure or by back siphonage.
The degree of hazard, either high, moderate, or low, is based on the nature of the contaminant; the potential of the health hazard; the probability of the backflow occurrence; and the effect on waterworks structures, equipment, and appurtenances used in the storage, collection, purification, treatment, and distribution of pure water.
Table 2.10 shall be used as a guide to determine the degree of hazard for any situation.
A. Air gaps give the highest degree of protection and shall be used whenever practical to do so in high hazard situations subject to back pressure.
B. An air gap separation and a reduced pressure principle backflow prevention device will protect against back pressure when operating properly. Vacuum breakers will not protect against back pressure, but will protect against back-siphonage when operating properly.
C. Backflow prevention devices consisting of dual independent check valves with or without an intermediate atmospheric vent shall only be used in low hazard situations.
D. Barometric loops are not acceptable.
E. An interchangeable connection or change-over device has limitations which prevent its use where back pressure is present or may occur, the auxiliary supply is not an approved source, or the waterworks line pressure is less than 20 psi. Since this type connection is one of the easiest to bypass, the use of this type device will be approved only as a temporary and continuously supervised arrangement. In most instances, an approved device or method must be included and approved by the purveyor and division.
F. Reduced pressure principle type backflow preventers shall not be installed in pits or areas subject to flooding.
Historical Notes
Derived from VR355-18-006.05 § 2.29, eff. August 1, 1991; amended, Volume 09, Issue 17, eff. June 23, 1993.