Table I
Minimum Airgaps for Generally Used Plumbing Fixtures
| |||
---|---|---|---|
Minimum Airgap
| |||
Fixture
|
When Not Affected by Near Wall1
(inches)
|
When Not Affected by Near Wall2
(inches)
| |
Lavatories and other fixtures with effective openings not greater
than 1/2 inch diameter
|
1.0
|
1.50
| |
Sink, laundry trays, goose-neck bath faucets and other fixtures
with effective openings not greater than 3/4 inch diameter
|
1.5
|
2.25
| |
Over rim bath fillers and other fixtures with effective openings
not greater than 1 inch diameter
|
2.0
|
3.0
| |
Drinking water fountains - single orifice 7/16 (0.437) inch
diameter or multiple orifices having total area of 0.150 square inch
(area of circle 7/16 inch diameter)
|
1.0
|
1.50
| |
Effective openings greater than 1 inch
|
3
|
4
|
NOTES:
| ||
---|---|---|
1
|
Side walls, ribs, or similar obstructions do not affect airgaps
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.
| |
2
|
Vertical walls, ribs, or similar obstructions extending from
the water surface to or above the horizontal plane of the spout opening
require a greater airgap 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 airgap shall be measured from the top of the wall.
| |
3
|
Two times diameter of effective openings.
| |
4
|
Three times diameter of effective openings.
|
Table II
Sizes of Overflow Pipes for Water Supply Tanks
| ||
---|---|---|
Minimum Capacity of Water Supply Line to Tank
(gpm)
|
Diameter of Overflow Pipe
(inches ID)
| |
0 to 50
|
2
| |
50 to 150
|
2 1/2
| |
100 to 200
|
3
| |
200 to 400
|
4
| |
400 to 700
|
5
| |
700 to 1,000
|
6
| |
Over 1,000
|
8
|
Table III
Cross-Connections Where Protective Devices are Required
and Critical Level (C-L) Settings for Vacuum Breakers1
| ||
---|---|---|
Fixture or Equipment
|
Method of Installation
| |
Aspirators and ejectors
|
C-L at least 6 inches above flood level of receptacle served
| |
Dental units
|
On models without built-in vacuum breakers: C-L at least 6 inches
above flood rim of bowl
| |
Dishwashing machines
|
C-L at least 6 inches above flood level of machine; install
on both hot and cold water supply line
| |
Flushometers (closet & urinal)
|
C-L at least 6 inches above top of fixture supplies
| |
Garbage can cleaning machine
|
C-L at least 6 inches above flood level of machine; install
on both hot and cold water supply lines
| |
Hose outlets
|
C-L at least 6 inches above highest point on hose line
| |
Laundry machines
|
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
| |
Steam tables
|
C-L at least 6 inches above flood level
| |
Tank and vats
|
C-L at least 6 inches above flood level rim or line.
| |
Trough urinals
|
C-L at least 30 inches above perforated flush pipe.
| |
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
| |
Hose bibbs (where aspirators or ejectors could be connected)
|
C-L at least 6 inches above flood level of receptacle served
|
NOTES:
| ||
---|---|---|
1
|
"Critical 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.
|
Table IV
Partial List of Cross-Connections Which
May Be Subject to Backpressure
| ||
---|---|---|
Chemical lines
|
Pressure tanks
| |
Dock water outlets
|
Pumps
| |
Individual water supplies
|
Steam lines
| |
Industrial process water lines
|
Swimming pools
| |
Hose bibs
|
Tank and vats-bottom inlets
|