Minimum Air Gaps for Generally Used Plumbing
Fixtures
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Fixture
|
Minimum Air Gap
(inches)
When Not Affected by Near
Wall1
|
When Affected by Near Wall2
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Lavatories and other fix- tures with effective
openings not greater than 1/2 inch in diameter
|
1.0
|
1.50
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Sinks, laundry trays, goose- neck bath faucets
and other fixtures with effective openings not greater than 3/4 inch
in diameter
|
1.5
|
2.25
| |
Over-rim bath fillers and other fixtures with
effective openings not greater than 1 inch in diameter Fixture
|
2.0 Minimum Air Gap (inches) When Not Affected
by Near Wall1
|
3.0 When Affected by Near Wall2
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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
|
1.50
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Effective openings greater than 1 inch
|
Note 3
|
Note 4
|
NOTES:
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1Sidewalls, ribs
or similar obstructions do not affect air gaps when spaced from inside
edge of 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 spout opening
than specified in Note 1 above. The effect of three or more such vertical
walls or ribs has not been determined. In such cases, the air gap
shall be measured from the top of the wall.
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3Two times diameter
of effective opening.
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4Three times diameter
of effective opening.
|
Control Devices
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Condition
|
Air Gap
|
Reduced Pressure Device
|
Double Check Valve Assembly
|
Atmospheric Breaker
|
Pressure Vacuum Breaker
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Any physical connection which may be subject
to back pressure involving:
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Hazardous substances1
|
X
|
X
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Nonhazardous substances2
|
X
|
X
|
X
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Any physical connection not subject to back
pressure involving:
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Hazardous substances1
|
X
|
X
|
X
|
X
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Nonhazardous substances2
|
X
|
X
|
X
|
X
|
X
|
NOTES:
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1A hazardous substance
includes sewage, lethal chemicals or other substances which, if introduced
into the public water supply system, would or may endanger the health
of the consumer.
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2A nonhazardous substance
would not endanger the health of the consumer but would be a nuisance
if introduced into the public water supply system.
|
Cross-Connections Where Protective Devices
Are Required and Critical Level (C-L) Settings for Vacuum Breakers
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Fixture or Equipment
|
Method of Installation
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Aspirators and ejectors
|
C-L at least 6 inches above flood level of receptacle
served
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Dental units
|
C-L at least 6 inches above flood level of machine.
Install on both hot- and cold-water supply line.
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Models without built-in 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 supplied
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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 line.
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Hose outlets Cross-Connections
|
C-L at least 6 inches above highest point on
hose line
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Laundry machines
|
C-L at least 6 inches above flood level of machine.
Install on both hot- and cold-water supply lines.
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Lawn sprinklers
|
C-L at least 12 inches above highest sprinkler
or discharge outlet
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Steam tables
|
C-L at least 6 inches above flood level
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Tank and vats
|
C-L at least 6 inches above flood-level rim
or line
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Trough urinals
|
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)
|
C-L at least 6 inches above flood level of receptacle
served
|