Originally Posted By: bbadger
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No easy NEC answers.
If we are talking about just
bonding the metal water piping system that can be done anywhere on the water piping system.
If we are talking about using the water piping as a grounding electrode then that connection must be within 5' of the entrance.
I will try to give some examples.
A building is served by a plastic water pipe from the water company once inside the building the pipe is copper.
We can not use the water pipe as a grounding electrode because the underground section is plastic.
In this case all we will do is bond
the interior metal piping at any location, this ensures the interior metal piping is not energized by a faulty piece of equipment like an electric water heater or any number of other appliances etc.
A building is served by a metal water pipe from the water company once inside the building the pipe is plastic.
In this case the underground water pipe qualifies as a grounding electrode and we must run a grounding electrode conductor to it within 5' of the entrance.
Why must it be close to the entrance?
Added safety for those working on the water lines inside the house.
A water pipe used as the grounding electrode often has current flowing through it. If you separate the pipe to work on it between the street side and the point the grounding electrode conductor is connected you are very likely to get a shock.
This is also one of the reasons items like water meters must have bonding jumpers around them.
Electrical Construction & Maintenance
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