Why use water main as grounding electrode?

[jselesk2]

Hi guys,

I understand that it is permissible to use the water main as a grounding electrode as long as it is in direct contact with earth for at least 10 ft and the GEC is clamped to water main within first 5ft of entering the building. I have two specific questions regarding this:

1) If the water main is used as a grounding electrode, how many other supplementary GE's are required?
2) Why would anyone use a water main as a grounding electrode instead of simply using two 8' ground rods?

Bonus Question) Is it always necessary to make a continuous connection from the water main pipe (at building entrance) to the main panel neutral bar regardless of the number of GE's used?

 

[JFletcher]

The answer to your first and second question is in sections 250.52 and 250.56.

The bonus question is under 250.64 C

 

[augie47]

The answer to your first and second question is in sections 250.52 and 250.56.

The bonus question is under 250.64 C

and maybe 250.50 "all grounding electrodes... where present...shall be bonded together.." so not getting your job rejected is one reason to use it.

 

[Dennis Alwon]

IMO, a water pipe is a better electrode then 2 rods, in most cases anyway. The water main must be supplemented one time. However, all electrodes shall be bonded together. This does not mean they all must be continuous. The wire to your first electrode must be continuous and the rest just bonded together wth bonding jumpers

 

[kwired]

If the pipe is exactly 10 feet long - it may not be much different then a rod or pair of rods, but the larger diameter the pipe is the more surface area it will have and will become an even lower resistance electrode.

Most of the time they are longer then 10 feet though, and likely have a lower resistance then a pair of rods will have.

 

[roger]

and maybe 250.50 "all grounding electrodes... where present...shall be bonded together.." so not getting your job rejected is one reason to use it.

IMO, a water pipe is a better electrode then 2 rods, in most cases anyway. The water main must be supplemented one time. However, all electrodes shall be bonded together. This does not mean they all must be continuous. The wire to your first electrode must be continuous and the rest just bonded together with bonding jumpers

:thumbsup:

Roger

 

[Besoeker]

2) Why would anyone use a water main as a grounding electrode instead of simply using two 8' ground rods?

Because it's there?

 

[JFletcher]

Because it's there?

Pretty much. 250.50 requires you to use it, if present.

 

[electrofelon]

Hi guys,

I understand that it is permissible to use the water main as a grounding electrode as long as it is in direct contact with earth for at least 10 ft and the GEC is clamped to water main within first 5ft of entering the building. I have two specific questions regarding this:

1) If the water main is used as a grounding electrode, how many other supplementary GE's are required?
2) Why would anyone use a water main as a grounding electrode instead of simply using two 8' ground rods?

Bonus Question) Is it always necessary to make a continuous connection from the water main pipe (at building entrance) to the main panel neutral bar regardless of the number of GE's used?

It seems your questions have been answered. But here is something else to think about: Bonding the water line is a huge pet peeve of mine. Because of our MGN system (not all, but most places) and lack of dielectric unions, we usually have neutral current flowing on the water line, both in the house and in the whole municipal system. This is the same thing the NEC goes crazy trying to avoid pretty much everywhere else in the code. They did away with the three wire feeder to remote structures because of this :rant: Of course there is no easy solution, as a fix would require coordination with other systems/trades and/or a non MGN system and a transformer only supplying one structure.

 

[JFletcher]

Electrofelon, without that water pipe Bond, a lot of older houses would have already fried their Electronics due to a bad neutral on the Service drop. Intentional or not, the water pipe Bond provides a secondary neutral. Putting a jumper around the meter to save the plumber from a potentially nasty shock is not a solution.

I have much the same issues with bonding the coax and cable to the main panel... If you lose a service neutral, and have plastic piping and the no water pipe bond, the neutral current from the house will attempt to flow through the coax, and most definitely fry it all.

 

[electrofelon]

Electrofelon, without that water pipe Bond, a lot of older houses would have already fried their Electronics due to a bad neutral on the Service drop. Intentional or not, the water pipe Bond provides a secondary neutral. Putting a jumper around the meter to save the plumber from a potentially nasty shock is not a solution.

I have much the same issues with bonding the coax and cable to the main panel... If you lose a service neutral, and have plastic piping and the no water pipe bond, the neutral current from the house will attempt to flow through the coax, and most definitely fry it all.

I like the setup I have: Utility distribution is ungrounded delta. I have my own isolated supply. MY electrons go back to MY transformer on MY neutral! Its not like trying to keep a cat in a bathtub with where your electrons go. Granted you would still have these issues where one transformer feeds several structures as is common in the population centers......

 

[JFletcher]

Continental Cablevision, the cable company that cabled all of the houses in my area back in the early 80s, they drove 1 ground rod at the demarc, ran a 14 gauge wire to it from the first splitter, and called it a day. No bonding to service whatsoever. I have never seen any issue with any of these installed regarding lightning strikes, fried Electronics, or shocks from equipment at different potentials.

People now may think that is hack, but far from it... They used embossed cable and compression fittings that is some of the most beautiful work and materials I've ever seen.

For some reason, this bit of trivia was not on VH1 show I love the 80s... LOL

 

[kwired]

It seems your questions have been answered. But here is something else to think about: Bonding the water line is a huge pet peeve of mine. Because of our MGN system (not all, but most places) and lack of dielectric unions, we usually have neutral current flowing on the water line, both in the house and in the whole municipal system. This is the same thing the NEC goes crazy trying to avoid pretty much everywhere else in the code. They did away with the three wire feeder to remote structures because of this :rant: Of course there is no easy solution, as a fix would require coordination with other systems/trades and/or a non MGN system and a transformer only supplying one structure.

It may often end up bonded through some EGC anyway - may of may not be a solid bond when this happens.

 

[jaggedben]

In places where the entire underground water system was or still is metal, using the water pipe actually creates a low impedance connection to the earth. Two rods, by comparison, does didley squat. If your neighbors' houses are also grounded to the metal water pipe system then that provides protection from damage due to an open neutral (although it also masks the problem).

Lots of places don't have metal water distribution anymore but most did at one point, which explains the history of using it.