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All Single • Double A9. PIPING AND SUMP CLEARANCES A10. PILLIN a TANKS Tanks with Bottom Sumps When installing a tank equipped with a bottom sump, ex- cavating and bedding must be modified to provide: Do not fill tank with product or water for hold-down until backfilling Is even with top of tank or tank damage can ♦ A hole centered at the sump location. occur. ♦ Hole should be 12" deep x 24" diameter. Exception - "Installation Procedure-Wet Hole" section. After the tank is placed,the void surrounding the sump must be: ♦ Hand backfilled and All. VENTING ♦ Hand tamped prior to adding backfill around tank or ♦ All tanks must be vented. use a long handled curved probe to fill hole. ♦ Tanks are designed for operation at atmospheric pres- External Piping sure only (except for use with vapor recovery systems ♦ The pump and attached piping must be free to move provided the pressure or vacuum does not exceed 1 psi.) with the tank (see figure 23). ♦ The vent opening should be the same diameter or larger ♦ Use a fill box or street box to isolate the piping from the than the piping used to remove product. traffic pad. ♦ For double-wall tanks, if the annular space is vented, it ♦ Take precaution during construction to make sure no must be vented independently from the primary tank. damage occurs to the exposed piping and fittings. ♦ For hydrostatically monitored double-wall tanks,the an- FIGURE 23 nular space must be vented at all times. External Piping IsolatePiping .. PRESSURIZED PRODUCT DELIVERIES from Traffic CAUTION :Slabs: Pressurized product deliveries are not recommended AS TANK DAMAGE MAY OCCUR. ♦ If the delivery vehicle uses pumps to fill the tank: ❑ Install overfill,shut-off equipment in the lines and on the truck to prevent the tank from being overfilled. Internal Piping ❑ Overfilling the tank under pressure will damage ♦ Internal piping must terminate a minimum of: the tank,even if the tank vent is unrestricted. ❑ 4"from the tank bottom(4',6',8', 10'diameter tanks). ❑ Do not use a ball float valve for overfill protection. ❑ 6" from tank bottom (12' diameter tanks). (see figure 24) Al2. MANWAY AND MANWAY EXTENSIONS ♦ A fill tube insert must be installed at the tank gauging fitting if the manual dipstick method is used to inven- tory tanks to ensure the dipstick point of impact is aligned with the tank bottom protector plate. Do Not enter tank unless following OSHA guideilnea FIGURE 24 for confined space entry. Internal Piping Entry Can Result in: 4'-10' 12' dia. dia. Tanks Tanks Oct 4"min 6"min / ASPHYXIATION FIRE EXPLOSION CONTINUED ON PAGE 16 15