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pei.org 9 Recommended Practices for the Testing and Verification of Spill, Overfill, Leak Detection and Secondary Containment Equipment at UST Facilities CAUTION: Use only an air-operated vacu- um source or a vacuum pump powered by an explosion-proof motor. Vacuum pumps with electric motors that are not explo- sion-proof may ignite flammable vapors. If a portable air compressor is used, it should be located at least 20 feet away from the venturi-eductor or outside any Class I, Division 1 area. 4.2.4 Preparation. The procedures in this sec- tion are general in nature and reflect the suggested vacuum levels and hold times for testing tank secondary containment areas. Consult tank manu- facturer and authority having jurisdiction (AHJ) guidelines before performing these tests, as their requirements may differ. Determine if there is liquid present in the intersti- tial space. If liquid is found, determine if the fluid is water or product, and remove it to the extent practicable. The hydrostatic pressure from a high water table imposes inward pressure on the outer wall of a UST. Applying a vacuum to the interstitial space of the tank creates additional pressure on the outer wall. These combined forces can damage the secondary tank wall when there is a large defined space between the primary and secondary tanks. Consequently, to prevent damage to the tank, it is important to observe the water table and associated recommended vacuum levels when testing. Vent the primary tank to atmosphere during the test. In some installations, the tank interstitial space may be vented to minimize the buildup of conden- sation. In these cases, seal off any vent lines to the tank interstitial space prior to testing. Determine the volume of the tank. This informa- tion is available from facility records or the auto- matic tank gauge (ATG) readout. 4.2.5 Steel Tanks. Determine if the interstitial space is a “tight-wrap” design or a “110% contain- ment” design. Tanks with a 110% containment design should use the latest version of Steel Tank Institute’s (STI) R012, Recommended Practice for Interstitial Tightness Testing of Existing Under- ground Double Wall Steel Tanks for testing. For tight-wrap tanks, use the test method in this section. 4.2.6 Fiberglass Tanks. Determine if the inter- stitial space is a “tight-wrap” design or a “110% containment” design. Either type of fiberglass tank may use this test or the latest version of Fiberglass Tank & Pipe Institute’s (FTPI) RP 2007, Field Test Protocol for Testing the Annular Space of Installed FIGURE 4-4. The plumber’s plug provides a leak-tight connection to draw a vacuum on the tank interstitial space. FIGURE 4-3. The vacuum gauge and control valve used for tank interstitial testing.F