Certification

Leak rate of 0.2 gph with PD = 98.18% and PFA = 1.82% using 924/B probe with 2” dia float.
Leak rate of 0.2 gph with PD = 95.28% and PFA = 4.72% using 924/B probe with 4” dia float.
Leak rate of 0.1 gph with PD = 95.9% and PFA = 4.1% using 924/B probe with 2” dia float.
Leak rate of 0.1 gph with PD = 96.5% and PFA = 3.5% using 924/B probe with 4” dia float.  

Leak rate of 0.2 gph with PD = 98.1% and PFA = 1.9% using Q0400-4xx probe with 4" dia float.

Leak Threshold

0.1 gph for leak rate of 0.2 gph using 924/B or Q0400-4xx probe for 2” dia and 4” dia floats. 
0.033 gph for leak rate of 0.1 gph using 924/B probe with 2” dia float.
0.05 gph for leak rate of 0.1 gph using 924/B probe with 4” dia float.
A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds this threshold.

Applicability

Gasoline, diesel, aviation fuel.

Tank Capacity

Maximum of 20,000 gallons. 
Tank must be minimum 50% full for leak rate of 0.2 gph using 924/B or Q0400-4xx probe.  
Tank must be minimum 90% full for leak rate of 0.1 gph using 924/B probe.

Waiting Time

Minimum of 6 hours between delivery and testing using 924/B or Q0400-4xx probe. 
There must be no delivery during waiting time.

Test Period

Average data collection time of 30 minutes using 924/B probe for leak rate of 0.2 gph.
Minimum of 6 hours using 924/B probe with 2” dia float for leak rate of 0.1 gph.
Minimum of 1.5 hours using 924/B probe with 4” dia float for leak rate of 0.1 gph.

Minimum of 4 hours for using Q0400-4xx probe with 4" dia float for leak rate of 0.2 gph.
Test data are acquired and recorded by system's computer.  
There must be no dispensing or delivery during test.

Temperature

Average for product is determined by a probe containing 5 thermistors.  5 resistance temperature detectors (RTDs) for Q0400-4xx probes.

Water Sensor

Minimum detectable water level that can be detected by the 2” dia float is 0.75 inch.  
Minimum detectable water level that can be detected by the 4” dia float is 0.848 inch.
Minimum detectable change in water level that can be detected by the 2” dia float is 0.080 inch.
Minimum detectable change in water level that can be detected by the 4” dia float is 0.043 inch.

Calibration

Thermistors (or RTDs) and probe must be checked and, if necessary, calibrated in accordance with manufacturer's instructions.

Comments

Not evaluated using manifolded tank systems.
Therefore, this certification is only applicable when there is a probe used in each tank and the siphon is broken during testing. 
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.