The problem is when the merchant stores idle wood pallets higher than 6 feet. At this point, NFPA 13 requires NFPA 231 for protection requirements. Wood pallets stored from 6 feet to 8 feet in height will require that the portion of the sprinkler system above the pallet storage area, and an additional 15 feet beyond the storage area, be protected with a delivered density of .30 over 2500 square feet-using 286 F sprinklers. Higher than an 8 foot storage will require a density of .60 gpm over 3500 square feet. This is beyond the capability of most of the systems that are designed and installed in most mercantile facilities.
Plastic pallets present an even greater hazard.
Without additional protection, they can only be stored to 4 feet in height and no more than two pallet stacks per pile. Beyond that, they are required to be stored in cutoff rooms, a density of .60 for the entire cutoff room and a maximum storage height of 12 feet. This same question also applies to the check valve on the system side of a fire pump. This is NOT an acceptable practice. The tests that a BFP is subjected to as part of its listing are significantly different from those applied to a check valve.