Roger...if the cold water pipe is for connection of the GEC then it must be sized according to table 250.66 which would probally be a #4 copper for a 200 amp SE cable and if it were just a metal water pipe bond then it also must be sized according to table 250.66 except as permitted in 250.104(A)(2) and (A)(3)
250.104(B) is for "other metal piping"
