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Determining Drop Tube Length Defender Spill Containment(Ref.) i a To find Upper Drop Tube length"X" To of Riser „A" r Riser Length «A„ + (add) Tank Riser Pipe "X» Top of Tank "B" r Offset - (subtract) Overfill Prevention Valve 1 rr Position and 2/2 mounting adjustment) 18'/4 =(equals) 95%of Tank Volume Offset (From Tank Chart) X„Upper Drop Tube Length To find Lower Drop Tube length"Y” (U.S.T.) „C„ Riser to tank bottom ower - (subtract) Drop Tube rr , rr Upper Drop aY» X1 Tube Length - (subtract) 18'/4' OPV 1 Length - (subtract) VTank bottom I 6" clearance 1 =(equals) 6" (152 mm) Max* "Y" Lower Drop Tube Length Bottom of Tank Not to Scale To find Tank Volume Offset * If local codes require this distance to be smaller, subtract less than 6" Tank Capacity Figure 1:Installation Overview and Drop Tube Calculation X .05 5%Volume (Correlate this number 5% Height with the tank chart) Q = B Explanation of Figure 1 Dimensions A • Distance from the seat surface of the upper drop tube to the inside of the top of the tank. The seat surface will vary depending on the type of installation (see Figure 2). • If this is a manway application, be sure to include the height of the manway to the inside of the top of the tank B • 95% tank volume offset—obtained from the tank chart provided by the tank manufacturer. This is typically equal to the 5% level measurement. To find the 5% tank level on the tank chart, multiply the full tank capacity by .05. Then find on the tank chart the level measurement that matches the calculated volume the closest. If this is a manway application, be sure to include the height of the manway to the inside of the top of the tank. • If tank tilt is an issue, the installing contractor may use best judgment to adjust"B"dimension accordingly, so "... none of the fittings located on top of the tank are exposed to product due to overfilling," per EPA 40CFR280 C I • Distance from the seat surface of the upper drop tube to the bottom of the tank 4