Issue Date:  October 5, 2015
Revision Date:  September 10, 2019

Purpora Engineering, Inc.

Alert 8200 Series Underfill Method



Leak rate of 0.1 gph with PD = 99.58% and PFA = 0.42% for 1 hour test

Leak Threshold

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.


Gasoline, diesel, aviation fuel, fuel oil #4, waste oil, biodiesel blends B6-B20 meeting ASTM D7467, biodiesel B100 meeting ASTM D6751 and water. The principle of mass displacement testing allows the operator to adjust the weight of the test probe in proportion to the specific gravity of the test liquid.

Tank Capacity

Maximum of 30,000 gallons.
Tank must be between 16% (with a fuel height of 14” or more) and 95% full.

Waiting Time

Minimum of 3 hours 41 minutes between delivery and testing.
There must be no delivery during waiting time.

Test Period

Minimum of 1 hour 28 minutes to achieve PD = 99.58% and PFA = 0.42%.
Test data are acquired and recorded by system's computer.
Leak rate is calculated from the data determined to be valid by statistical analysis.
There must be no dispensing or delivery during test.


System measures product mass (which is not affected by temperature) instead of product volume.


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 0.2 psi pressure differential between the water table and fuel level at the bottom of tank during test.
If no water table info available, two tests are required at different product heights of different tank pressures.

Calibration Load cell must be calibrated at least once per year following manufacturers recommended practices, but not necessarily by manufacturer.


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.
The manufacturer does not support test results if the technician does not hold a current Pupora Enginerring certification when the test is performed. Recertification is required by the manufactuer every two years.



Purpora Engineering Inc.

Evaluator:  Ken Wilcox Associates

658 North Progress Drive

Tel:  (816) 443-2494

Saukville, WI 53080

Dates of Evaluation:  09/14/15

Tel:  (262) 536-4081







 | Home | Vendors: A - F | Vendors: G - M | Vendors: N - S | Vendors: T - Z | Method Index | Glossary |

Appearance on this list is not to be construed as an endorsement by any regulatory agency nor is it any guarantee of the performance of the method or equipment.
Equipment should be installed and operated in accordance with all applicable laws and regulations.  For full details, please refer to our expanded "DISCLAIMER" page.