Table I
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Minimum Air Gaps for Generally Used Plumbing
Fixtures
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Minimum Air Gap
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When Not Affected By Near Wall1
(inches)
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When Affected By Near Wall2
(inches)
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Lavatories and other fixtures with effective
openings not greater than 1/2 inch in diameter
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1.0
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1.50
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Sinks, laundry trays, gooseneck bath faucets
and other fixtures with effective openings not greater than 3/4 inch
in diameter
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1.5
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2.25
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Over-rim bath fillers and other fixtures with
effective openings not greater than 1 inch in diameter
|
2.0
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3.0
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Drinking water fountains: single orifice 7/16
(0.437) inch in diameter or multiple orifices having total area of
0.150 square inch (area of circle 7/16 inch in diameter)
|
1.0
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1.50
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Effective openings greater than 1 inch
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See Note 3
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See Note 4
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NOTES:
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1Side walls, ribs
or similar obstructions do not affect air gaps when spaced from the
inside edge of the spout opening a distance greater than three times
the diameter of the effective opening for a single wall or a distance
greater than four times the diameter of the effective opening for
two intersecting walls.
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2Vertical walls,
ribs or similar obstructions extending from the water surface to or
above the horizontal plane of the spout opening require a greater
air gap when spaced closer to the nearest inside edge of the spout
opening than specified in Note 1 above. The air gap shall be measured
from the top of the wall.
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3Two times the diameter
of the effective opening.
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4Three times the
diameter of the effective opening.
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Table II
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Size of Overflow Pipes for Water Supply
Tanks
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Maximum Capacity of Water Supply Line
to Tank
(gallons per minute)
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Diameter of Overflow Pipe
(inches inside diameter)
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0 to 50
|
2
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50 to 150
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2 1/2
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150 to 200
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3
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200 to 400
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4
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400 to 700
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5
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700 to 1,000
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6
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Over 1,000
|
8
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Table III
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Cross-Connections Where Protective Devices
Are Required and Critical Level (C-L) Settings for Vacuum Breakers1
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Fixture or Equipment
|
Method of Installation
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Aspirators and ejector
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C-L at least 6 inches above flood level of receptacle
served
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Dental units
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On models without built-in vacuum breakers C-L
at least 6 inches above flood-level rim of bowl
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Dishwashing machines
|
C-L at least 6 inches above flood level of machine;
install on both hot and cold water supply line
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Flushometers (closet and urinal)
|
C-L at least 6 inches above top of fixture supplies
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Garbage can cleaning machine
|
C-L at least 6 inches above flood level of machine;
install on both hot and cold water supply lines
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Hose outlets
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C-L at least 6 inches above highest point on
hose line
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Laundry machines
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C-L at least 6 inches above flood level of machine;
install on both hot and cold water supply lines
|
Lawn sprinklers
|
C-L at least 12 inches above highest sprinkler
or discharge outlet
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Steam tables
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C-L at least 6 inches above flood level
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Tank and vats
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C-L at least 6 inches above flood-level rim
or line
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Trough urinals
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C-L at least 30 inches above perforated flush
pipe
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Flush tanks
|
Equip with approved ball cock; where ball cocks
touch tank water equip with vacuum breaker at least 1 inch above overflow
outlets; where ball cock does not touch tank water install ball cock
outlet at least 1 inch above overflow outlet or provide vacuum breaker
as specified above
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Hose bibbs (where aspirators or ejectors could
be connected)
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C-L at least 6 inches above flood level of receptacle
served.
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NOTES:
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1Critical level (C-L)
is defined as the level to which the vacuum breaker may be submerged
before backflow will occur. Where the C-L is not shown on the preventer,
the bottom of the device shall be taken as the C-L.
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Table IV
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Partial List of Cross-Connections Which
May Be Subject to Backpressure
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Chemical lines
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Pumps
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Dock water outlets
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Steam lines
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Individual water supplies
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Swimming pools
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Industrial process waterlines
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Tank and vatsbottom inlets
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Pressure tanks
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Hose bibbs
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