Issue Date: August 23, 1999
Revision Date: January 24, 2008

Steel Tank Institute

Permatank Interstitial Vacuum Monitor Liquid Leaks


Certification Leak rate of 0.1 gph with PD = 100% and PFA < 5%.
Leak Threshold A tank system should not be declared tight when the vacuum decreases (pressure increases) 5 inches or more of mercury over the test period specified for each tank size. 
Vacuum prior to test must be minimum of 14 inches of mercury.
Applicability Gasoline, diesel, water.
Tank Capacity Maximum of 20,000 gallons. No minimum product level during test.
Waiting Time None between delivery and testing.
Test Period Test periods required for selected tank sizes to detect a leak rate of 0.1 gph

Selected Tank Sizes




500 gal

0.4 hr

5.0 hr

4.8 hr

5,000 gal

1.3 hr

16.2 hr

15.7 hr

8,000 gal

2.1 hr

24.9 hr

24.2 hr

20,000 gal

3.7 hr

44.8 hr

43.6 hr


System tests the interstitial space between inner steel wall and outer fiberglass wall of Steel Tank Institute's Permatank.
System detects breaches in either inner or outer tank walls.
System can perform tank tightness testing of Steel Tank Institute's double wall Permatank after product has been added to the primary tank.
System was not evaluated for ability to detect layer of hydrocarbons on water.
Evaluation did not cover any liquid sensors.


Steel Tank Institute

Evaluator:  Ken Wilcox Associates

570 Oakwood Rd.

Tel:  (816) 443-2494

Lake Zurich, IL 60047

Date of Evaluation:  04/24/94

Tel:  (847) 438-8265



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