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UST Program - LG 113

UST Programs - LG 113

Issue Date: August 23, 1999 


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. 
Interstitial space is tested continuously. 
System detects breaches in either inner or outer tank walls. 
System was not evaluated for ability to detect layer of hydrocarbons on water. 
Evaluation did not cover any liquid sensors.
This system may not be compatible with all secondarily contained tanks and/or piping. Always consult with the tank and/or piping manufacturer and the manufacturer's applicable recommended installation practices before installing this system, or damage may be caused to the tank or piping by its use.

State Waterboard staff are currently evaluating the applicability of this method in satisfying the performance standards for continuous vacuum/pressure monitoring systems required by Assembly Bill 2481 (Chapter 6.7, Health and Safety Code, section 25290.1). Listings will be updated once a determination has been made.


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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