Certification
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Leak
rate of 0.1 gph with PD = 100% and PFA = 0%.
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Leak
Threshold
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A
tank system should not be declared tight when the vacuum
decay is more than 1 inch water column pressure for non-volatile
products and 10% of the lower determined vapor pressure
for volatile products, or when water ingress is detected
by the water sensor.
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Applicability
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Gasoline,
diesel, aviation fuel, fuel oil #4, waste oil.
Other liquids may be tested after consultation with the
manufacturer.
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Tank
Capacity
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Maximum
of 12,000 gallons if groundwater is not present.
Maximum of 50,000 gallons if groundwater is present and
a vacuum of 1.0 to 1.7 psi can be maintained.
For gasoline, ullage volume must be between 800 and 2,500
gallons.
For diesel, ullage volume must be between 500 and 1,500
gallons.
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Waiting
Time
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None
between delivery and testing.
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Test
Period
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Minimum
of 2 hours, 30 minutes for gasoline (1 hour, 30 minutes
vapor equilibrium recirculation time* plus 1 hour test
period) when groundwater is below bottom of tank.
Minimum of 1 hour, 30 minutes for diesel and less volatile
products (30 minutes vapor equilibrium recirculation time*
plus 1 hour test period) when groundwater is below bottom
of tank.
Minimum of 1 hour when groundwater is above bottom of
tank.
Test period based on water ingress depends on tank size
and must be calculated in accordance with manufacturer's
instructions.
Test data are acquired and recorded manually.
*The vapor equilibrium recirculation time is the time
required to apply a vacuum and to saturate ullage with
vapors.
There must be no dispensing or delivery during test.
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Test
Pressure
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Vacuum
must be maintained between 1.0 to 1.7 psi at bottom of
tank.
Vacuum must not be greater than 4.0 psi in ullage.
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Temperature
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Vacuum
decay is independent of product temperature.
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Water
Sensor
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Conductivity
water sensor must be used to detect water ingress and
must be calibrated for every test.
Minimum detectable water level is 0.014 inch. Minimum
detectable change in water level is 0.0095 inch.
Minimum water level in tank must be adjusted to 0.014
inch before calibrating the sensor.
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Groundwater
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Per
California regulations, depth to groundwater in tank excavation
backfill must be determined.
If groundwater is above bottom of tank, water sensor must
be used and test time extended to ensure water ingress
detection during test.
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Comments
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Not
evaluated using manifolded tank systems.
Evaluated using gasoline and diesel.
Test may not be effective in some tank excavation backfill
(such as clay) because it may plug holes in tank.
If soil is saturated with product, air or water ingress
may not be detected by vacuum test.
A well point in tank excavation backfill may help identify
presence of this condition.
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