Issue Date: March 27, 2018

Leighton O’Brien

Wet Test



Calculated minimum detectable leak rate of 0.1 gph with PD = 99.99% and PFA = 0.0099% at 95% tank volume and the PD is greater than 97.31% at all other tank volumes.

Leak Threshold

Calculated leak threshold is 0.050 gph with PD = 95% and PFA = 5%.
A tank system should not be declared tight if the test result indicates a loss or gain that equals or exceeds this threshold


Gasoline, diesel, aviation fuel, fuel oil #4, solvents, waste oil, biodiesel blends B6-B20 meeting ASTM D7467, biodiesel B100 meeting ASTM D6751. 

Tank Capacity

Maximum size of tank = 20,000 gallons.

Waiting Time

Minimum of 2 hours and 59 minutes between delivery and testing.

Test Period

Minimum of 1 hour and 7 minutes.
There must be no dispensing or delivery during test.


If a test is to be conducted following a product delivery, the delivered product should not have temperature differences greater than ± 6.5 degrees F from the product already in the tank.


Depth to groundwater in tank excavation backfill should be determined if possible. If groundwater is above bottom of tank or is undetermined, then two passing tests are required at different product heights or different tank pressures to achieve a 1.5 psi differential. Conducting the Leighton O’Brien Wet Test and the Leighton O’Brien Dry Test (NVTTT Ullage) in combination will achieve this result.

Calibration Differential pressure sensor must be calibrated regularly in accordance with manufacturer's instructions.


This method was not evaluated with groundwater taken into account.
Tests only portion of tank containing product.
Not evaluated using manifolded tank systems. Testing can be conducted at product levels of 10 inches or greater.
Evaluated in a 13,750 gallon, horizontal fiberglass tank containing diesel fuel with a diameter of 120 inches and 323 inch length.



Leighton O’Brien

Evaluator:  Ken Wilcox Associates

3rd Floor, 20 Council Street

Tel:  (816) 443-2494

Hawthorn East, Victoria, Australia 3123

Dates of Evaluation: 12/01/2016

Tel: +61 3 9804 220







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