18.04 Is biocide still needed if filtration / polishing is used?

Biocide is still required in addition to filtration / polishing systems. While the filtration / polishing system minimizes the amount of water in the fuel, any trace amounts will accumulate in the bottom of the tank. The filtration / polishing pump, whether a suction style or a submersible, will not be effective in removing fluid from the bottom 3-6 inches of the tank.