Bonding with platic water pipe coming in

[binney]

Is there anything in the NEC which states that when bonding the copper water lines, (plastic water line coming in), that you have to put your clamp on a 3/4" or larger water line. I've bonded to 1/2" pipes in the past and have not had any problems. One of my "superiors" insists it has too be a 3/4" line, he insists that it has to be 3/4" cold hard water (before the water heater and the softner).

*Any code references would be appreciated.

Thank-you
Binney

 

[tom baker]

Re: Bonding with platic water pipe coming in

No there is not. Have you supervisor show you where it states it has to be minimum 3/4" line.
Start with section 250.52(A)(1). Bet an expensive dinner on this one as you are right.
If the water line meets the requirements of a grounding electrode it only needs be bonded with in 5 feet of the entrance.
However if the water line does not meet the ten feet in contact with the soil, you still connect to the water line, but now it becomes a bonding connection per 250.104.
Make sure you understand the difference.

 

[otm126]

Re: Bonding with platic water pipe coming in

Also be sure to install 2 ground rods for this service. I met all the requirements for the bonding but the inspector wanted 2 ground rods and I failed inspection. Tom's point is 100% correct

 

[pierre]

Re: Bonding with platic water pipe coming in

252.(A)(5) Rod and Pipe Electrodes.
here it mentions 3/4 trade size. That is where a lot of people think the 'so called' cold water pipe size requirement comes from. As the others have said, get yourself a good dinner out of this one

Pierre

 

[tom baker]

Re: Bonding with platic water pipe coming in

I was thinking about this issue of a minimum size for the water pipe. I have some small instrument shelters with a 60 amp service, and there is a water line, metallic, but it is 3/8" OD copper tube. I still bond to it, but there must be a miniumm current carrying capacity of copper water lines. Take for example a 500 amp service bonded to a 1/2" copper water line, will that 1/2" copper water line be equal in current carrying capacity to the grounding electrode conductor of 1/0?

 

[pierre]

Re: Bonding with platic water pipe coming in

I am sure that the capacity can be calculated, but the NEC does not require it nor does not seem to be concerned about it, remember the GEC is not for fault current.

Pierre

 

[charlie]

Re: Bonding with platic water pipe coming in

Pierre, it is not the intent of the NEC to require the water line to carry fault current. However, it will indeed carry fault current if the neighborhood is connected with a metallic water system. The fault current can flow through the GEC to the water line, through the metallic water system to your neighbor's home, through his GEC, through his service drop or lateral, and back to the transformer.

This will not happen to any great amount unless you have an open neutral since most of the return current will take the path of the phase conductors.

One of the problems we have had with old neighborhoods is to have an open neutral with the old ACSR conductor in a triplex service drop. It would go for years with no problems and would be found with routine service work or a service upgrade. We used to use #6 ACSR for the neutral of a #4 Al triplex and the galvanizing would be pitted. That would allow the steel to rust and separate, then the neutral would break. Needless to say, every time we come across an old 4/6 triplex, we replace it.

Tom, the current carrying ability of a metallic water line is immense with the water in the line. The water will act as a heat sink and, under fault conditions, the current will not be there for a long time unless you are waiting for the electric utility's transformer fuse to let go.