Corrosion of homes' copper water lines

[tinfoil]

I work for a electric utility.

We have just had at least 2 occurances of severe corrosion and pinholes in copper water lines supplying residential homes in a rural subdivision that is less thna two years old.

There is a local central water system using PVC pipes for their mains, and copper lateral lines to the houses. Building codes require electrical system bonding to the home's copper plumbing systems.

We have been asked by the Municipal Water Dept if this corrosion could be 'our fault'.

We have checked our system out. The padmounted transformers are properly grounded. The neutrals of all underground cables seem intact and are bonded at each transformer. There is virtually no voltage difference between neutral and ground at each affected home's meter base.

Anybody have any insight here? I am prepared to tell the water guys that we probably aren't the cause, but thought I'd get your opinions on this.

 

[GerH]

Can you determine if the corrosion is from inside to outside or vice-versa. Hole corrosion generally exhibits a decreasing hole diameter from the surface on the side the corrosion is active. Cases I have seen appear as if somebody took a drill and drilled just to the the point of break-through.

If it's inside to out the electric utility is probably in the clear.

The other aspect is pipe to soil potential. This is a measure of the half-cell difference with respect to a known reference. The usual half cell is Copper/Copper-sulphate and copper that is not being forced is about zero with respect to a Cu/C-S half cell