Water Main Grounding

[priendeau]

I was wondering if anyone knows of any documentation or reference info. available regarding the handling of metal (Cast iron, Ductile iron, Steel) water mains that may not be properly grounded. Is there a method required to protect water utliity operators from stray current from metal water mains (NOT water meters or service lines)? Someone I know was recently zapped good while working on an old cast iron water main that was beibng demolished near to a power company subsstation.

Thanks,

 

[don_resqcapt19]

Paul,
Actually it is the fact that the water line was properly bonded (grounded) to an electrical service that causes this problem. The electrcial code required connection to the metal underground water pipe puts the water pipe in parallel with the electrical service grounded (neutral) conductor. Under normal conditions some current will flow in the water pipe and small arcs can be observed if you break a connection in the water pipe. This will not be a hazard (remember I am talking about normal conditions here). However in cases where the grounded conductor is open or is a high impedance path, there is a serious shock hazard if a pipe connection is broken. There is no easy way to check for this hazard. I know that some plumbers make a bonding connection around the pipe joint before they break it to provide another path for the current.
There also could be a problem with the utilty substation that caused the shock.
Don

 

[haskindm]

To emphasize what Don said. You are talking about BONDING the water line. There is no need to ground a metallic object that is buried in the earth, it is already grounded. The problem is that electricity will take all available paths back to its source. One of these paths will be through a waterline that is properly bonded to the electrical service. This situation is magniifed if a neutral (grounded conductor) connection is lost, as the waterline may become the primary or even the only return path available. People working on water lines should be made aware of this possibility and steps should be taken to minimize the risk.