(2) A building backup caused by the blockage or failure of the building sewer or any other component of a plumbing system as defined in s. SPS 381.01(179), and discrete or individual building backups caused, or primarily caused, by excessive flow or hydraulic constraints within the sewage collection system shall not be subject to the requirements of s. NR 210.21(1). Note: Section SPS 381.01(179) reads: "Plumbing system" includes the water supply system, the drain system, the vent system, plumbing fixtures, plumbing appliances and plumbing appurtenances that serve a building, structure or premises.