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Plastic Water Piping
Posted by Robert from New York, NY, US on March 12, 2009
Code requires that interior metal piping be bonded to ground. When a (non-residential) building is plumbed using plastic pipe, but metallic faucets, handles, sinks, etc., what should be done? Is water conductive enough to trip circuit breakers? If a toaster fell into a metal sink, while water is running, could a person be shocked while washing hands at another washbasin (assuming actual or potential contact with grounded surroundings)?
Sec. 250.104(A)(2) says that "in buildings of multiple occupancy where metal water piping systems(s) installed in or attached to a building or structure for the individual occupancies is metalically isolated from all other occupancies by the use of nonmetallic water piping, the metal metal water piping system(s) for each occupancy shall be permitted to be bonded to the equipment grounding terminal of the panelboard or switchboard enclosure (other than service equipment) supplying that occupancy. I would assume that you have bonded the building's service to its metallic water service piping, as required by the NEC. Water is conductive, but whether it can conduct enough ground fault current to trip a circuit breaker is a good question. Your question about the toaster falling into a metal sink while water is running is moot, since it would probably be plugged into a GFCI receptacle, which trips on much smaller current.
