Certification
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Leak
rate of 0.1 gph with PD > 99% and PFA < 1.0%.
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Leak
Threshold
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0.05
gph.
A tank system should not be declared tight if the test
result indicates a loss or gain that equals or exceeds
this threshold.
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Applicability
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Gasoline,
diesel, aviation fuel, fuel oil #4.
Other liquids with known coefficients of expansion and
density may be tested after consultation with the manufacturer.
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Tank
Capacity
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Maximum
of 15,000 gallons.
Tank must be minimum 90% full.
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Waiting
Time
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Test
data are acquired and recorded by system's computer that
calculates a leak rate every minute, and determines waiting
time for satisfactory data (test is finished when the
standard deviation of 30 sequential leak rates is less
than half of the last leak rate determined).
There must be no dispensing or delivery during waiting
time.
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Test
Period
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Minimum
of 1 hour, 10 minutes.
Test data are acquired and recorded by system's computer.
Leak rate is calculated from data determined to be valid
by statistical analysis.
There must be no dispensing or delivery during test.
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Temperature
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Average
for product is determined by a minimum of 7 thermistors.
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Groundwater
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Depth
to groundwater in tank excavation backfill must be determined.
If groundwater is above bottom of tank, product level
must be adjusted to provide a minimum net pressure of
1 psi at bottom of tank during test.
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Calibration
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Level
sensor must be calibrated before each test.
Thermistors must be checked annually and, if necessary,
calibrated in accordance with manufacturer's instructions.
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Comments
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Not
evaluated using manifolded tank systems.
Tests only portion of tank containing product.
As product level is lowered, leak rate in a leaking tank
decreases (due to lower head pressure).
Consistent testing at low levels could allow a leak to
remain undetected.
EPA leak detection regulations require testing of the
portion of the tank system which routinely contains product.
System no longer being manufactured and no support is
available.
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