bit off water main

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boyle78

Senior Member
Location
new hampshire
Friday afternoon as we were walking out the door, we got a call about a guy that got bit when he took apart the water pipe in a building. I don't have much info since another co-worker took the call, but I am wodering how this would happen. I know the building was recently upgraded with a new transformer and ppl's. I was wondering if the transformer grounding/bonding would be a place to look. I only say this because it was mentioned after we got the call. I am being impatient for Monday or when I get a chance to check it our for myself and I realize it could be any number of things. I was just wondering if anyone has run into this and how they went about isolating the cause.
 

iwire

Moderator
Staff member
Location
Massachusetts
Where did he split the pipe?

If it was between the street and the GEC connection then you can almost always expect current flow.

If he split the pipe somewhere in the building I would look more into it.
 

iwire

Moderator
Staff member
Location
Massachusetts
according to the call, he was working on the meter as it came into the building.

That would do it and is pretty much normal.

Due to the buildings GEC connection and the utilities use of a multi-grounded neutral distribution system the metal water pipe is electrically parallel with the buildings service neutral.
 
We got a call that a plumber got zapped a good one cutting the water main to a home to replace it.

On inspection, the bare wire on the overhead drop from the POCO to the weatherhead had been chewed through by a squirrel, hence the only path to ground for the unbalanced load on the neutral was the grounding electrode conductor connected to the water line.

The plumber was actually pretty fortunate that he wasn't killed.
 

iwire

Moderator
Staff member
Location
Massachusetts
The open neutral is definitely a problem in need of fixing. :smile:

However even with a complete neutral there will normally be current flow on the water line on the street side of the GEC connection.
 

nakulak

Senior Member
I would have to assume that it wasn't bonded accross the metere or else that particular plumber had an awfully low resistance (or there is an awful lot of current goiing thru the meter)
 

iwire

Moderator
Staff member
Location
Massachusetts
I know I might sound stupid, but I thought this was avoided by bonding both sides of the meter?

The meter jumper is there to ensure continuity from one side of the meter to the other. If the jumper is left in place when the meter is removed the chances of getting 'bit' is pretty much eliminated.

However if the connection made by the GEC from the panel neutral to the water pipe is on the home side of the water meter and both the meter and jumper are removed there is a very good chance of getting bit if you where to grab both the home side and street side water lines.

BTW, there are no stupid questions about Article 250 and grounding. :)
 

iwire

Moderator
Staff member
Location
Massachusetts
could being bit be further avoided by shutting down any loads to reduce any unbalance on the neutral?


Yes, if you could eliminate all neutral imbalanced current the water pipe would not carry any current.

In most buildings supplied with a metal water piping system the water piping will always carry some percentage of the imbalanced neutral current.
 

iwire

Moderator
Staff member
Location
Massachusetts
I should also mention if a neighbors home has an open neutral the current on your water line may be originating from the neighbors service.

The path would be out of the neighbors home on the metal water line continuing to your home on the metal water line into your GEC and back to the power company transformer over your service neural.
 
In my example, the plumber was on the homeowner side of the meter, so a jumper bond wouldn't have changed a thing regarding the shock. (out here, the water meter is in a box next to the street)

This was an older home (60's era), and the water pipe was the only ground source (no ground rod). With a bonded neutral, and the neutral chewed through, all unbalanced current was flowing through the GEC.

Had the plumber turned off all the breakers in the home (or the main), he wouldn't have been shocked. Of course, he was using a sawzall to cut the water main.
 

iwire

Moderator
Staff member
Location
Massachusetts
In my example, the plumber was on the homeowner side of the meter, so a jumper bond wouldn't have changed a thing regarding the shock. (out here, the water meter is in a box next to the street)


You lost me, if the jumper was there everything would be at the same potential including the earth. :-?
 

jwelectric

Senior Member
Location
North Carolina
I always thought that plumbers carried a set of these with them just for the type work mentioned in this thread

jumper%20cables.jpeg
 

boyle78

Senior Member
Location
new hampshire
Got some more info on the install today. Apparently, the EC didn't bond the system at the transformer and went from the XO leg on the trans. to the water pipe...depending on which loads were on I got a reading of 8v to 120v
on the reidentified #6 (250.119?) There were two trans. installed right next to each other...one was done correctly, the other was not.
 

iwire

Moderator
Staff member
Location
Massachusetts
The transformer is required to be connected to the water line.

But bonding XO to the enclosure would have been a nice touch.
 
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