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TRU- IPppro'Rec ' s est. Xerxes DWr-II double wail tanks with the TRU-CHEKO system Diagram A option are factory-filled with a brine solution in the interstice g between the two tank walls.The brine also partially fills a Reservoir reservoir affixed to the top of the tank.This creates a hydrosta- Level Down tic pressure that enables owners/users to monitor both the primary tank and the secondary tank walls. The TRU-CHEK®system provides a simple and precise method to perform a tank-tightness test. It was developed in conjunc- tion onjunc tion with Dr. Robert Plunkett, Sc.D., consulting engineer(pro- fessor emeritus), University of Minnesota.TRU-CHEK®has 0 received third-party verification from Underwriters Laboratories. TRU-CHEK®testing meets the EPA criteria for tank-tightness testing, which states that a test must be able to detect a leak rate of 0.1 gallon per hour from any portion of the tank that routinely contains product.The test has a 95%probability of detection(PD)and a 5%probability of false alarm (PFA). In other words, out of 100 chances, the test detects leaks 95% of the time. The test must also account for the effects of thermal expan- sion or contraction of the product, vapor pockets, tank defor- mation, evaporation, condensation and the location of the Diagram B water table. TRU-CHEK®is capable of detecting a loss rate as small as the Reservoir NFPA 329 criteria of 0.05 gallons per hour. Level Down In addition, on extended tests, TRU-CHEK®testing offers 99% PD and I%PFA. O The TRU- H ®test offers significant benefits to the owner/operator: ].A wide range of tank sizes can be tested, including Xerxes DWT41 tanks up to 20,000 gallons. 2.Product can be dispensed during the 9546/546 test. 3.No waiting time is required to start the test as long as a fill of new product does not vary more than 20°F from the existing product temperature. How continuous monitoring works If both the inner and outer walls are Diagram C tight, the reservoir level will be stable. If there is a fracture in the inner wall ` -� Reservoir (Diagram A), the brine level in the reser- i /Level lip - voir will go down.The brine level will ^^ also go down if there is a leak in the Water e k Level outer wall (Diagram B). _ With a high-water table and"wet-hole" _�� /� Fracture conditions (Diagram C), a leak in the Outer Wall outer wall will cause the brine level to go up if the height of the water table above the leak is ®30%greater than the brine level above the leak. See Xerxes TRU-CHEK® Krochure for more etails. 16