I'm working on a a high-end hotel which will have a vertical turbine fire pump above a water storage tank.
Can we waive a minimum pump submerge depth by installing an anti-vortex plate between the pump's bell and the strainer?
The fire pump is a 1,500 gpm vertical-turbine type, located directly above the water tank. The tank depth is 6'-3" from the overflow bottom down to the tank floor. The water tank area is 2,408 sqft. The selected pump recommends 51.63-inches as a minimum submerge depth. This is in addition to a 12-inch clearance between the bottom of the strainer and the tank floor. The water level to be maintained inside the tank then must be 63.63-inches (95,511 gallons).
The remaining active volume in the tank after extracting the required volume will be 112,582 - 95,511 = 17,071 gallons. This is not enough to run the pump set for the required time under NFPA 13 2019 (Table 220.127.116.11 and 18.104.22.168.2).
Can adding an anti-vortex plate between the pump's bell and the strainer waive this minimum submerge depth? If not, what might be a recommended solution for this?
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