MIL-HDBK-1005/7A
7.5
Cross Connections and Backflow Prevention With Non-
potable Supplies. Refer to AWWA Manual M14, Recommended
Practice for Backflow Prevention and Cross-Connection Control.
For Air Force projects use AFI 32-1066.
7.5.1
Backflow. Backflow of waste or contaminated water
into the distribution system due to back -siphonage or
backpressure should be prevented.
7.5.1.1
Sources . Conditions under which backflow can occur
are given below. Such conditions should not be permitted.
a)
Improper plumbing designs.
b)
Direct connections with nonpotable supplies.
(1)
Improper pipeline interconnections.
(2)
Potable supply lines submerged in nonpotable
water.
(3) Direct connections of drains from sources
such as a fire hydrant or valve box to a storm or sanitary
sewer.
(4)
Improper connections by users.
c)
Improperly designed or constructed distribution
systems. These are systems within an area subject to flooding
or systems that may be too close to subsurface sources of
contamination, such as septic tanks, drain fields, sewers, and
cesspools. Any leakage combined with lower pressure in the
distribution system can cause backsiphonage.
d)
A backflow preventer installed in a location
subject to submergence.
7.5.1.2
Protection Against Contamination
a)
Design for the absolute minimum number of
b)
Provide siphon breakers in all plumbing systems.
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