Q. Are you required to bond isolated sections of metal water pipe that are connected to a nonmetallic water piping system?
A. No. An isolated section of metal pipe is not a metal water piping system. A metal water piping system must be bonded as required in 250.104(A)(1), (A)(2), or (A)(3). The bonding jumper must be copper where it is within 18 in. of the earth [250.64(A)], securely fastened to the surface on which it's mounted [250.64(B)], and adequately protected if exposed to physical damage [250.64(B)]. In addition, all points of attachment must be accessible [250.104(A)]. In addition, you're not required to bond isolated sections of metal water piping connected to a nonmetallic water piping system (Figure).
To remove dangerous voltage on metal parts from a ground fault, electrically conductive metal water piping systems, metal sprinkler piping, metal gas piping, as well as exposed structural steel members likely to become energized, must be connected to an effective ground-fault current path [250.4(A)(4)].