Electrolysis issue

[BHastings]

I have a new client with an estate home. They have three seperate coldwater feeds to the house; one on the south end, one in the middle, and one on the north end. They are having issues with pitting in the coldwater pipe run under the slab in the center section of the home only. I understand that they have had to rip up the floor twice in the last 5 years and replace a pipe. The plumber told them it was electrolysis and told them talk to an electrican. The electrican that wired the home does not want to be involved in finding a solution so I was asked look at the problem.

Three seperate underground water feeds from a single meter I am told was because of structural issues. I currently do not know if they and continiously fed underground with copper around the exterior of building or if there is PVC between the feed points.

I can tell you that I do not think the home itself is grounded properly. There is a 400Amp split main panel on the house but the ground wire is run in a pvc conduit along with a subfeed to the detached garage building where it loops through the load center and disappears out through a knockout in the panel. I can find no uffer/cw bond/gas bond at either building.

I think what I need to do is to tie all three feeds with a common bond back to the the main service so that I will have an equalateral plane. What I don't want is to be inducing an isolated problem into the other two areas of the home however. I am open to hearing everyones ideas.


I have read about ph balances and other water-bourne sources of pitting but I am not sure that is the correct route to examine if it is only happening in 1 out of 3 areas (6 areas is you include additional out -buildings).

 

[brian john]

Why would you replace copper with copper when you are having copper issues?

As for electrolysis ,

Check the water pipes for AC and DC current, use a high quality amp clamp with a good resolution at low current.

And read this.

Like when electricians cannot solve power quality issues they blame grounding, electrolysis is the term plumbers use when they have no clue.


http://www.copper.org/applications/plumbing/techcorner/electrolysis_cause_copper_tube_fail.html

If you neutral in the sub panel is NOT grounded and you have no neutral to ground shorts down stream of the main neutral ground bond any improvements in your ground electrodes you do will not make the matter worse.

As you read in the attached article AC current is generally not associated with copper piping issues.

 

[tom baker]

Its likely not a grounding issue, and more likely a water quality issue. Some water can be very aggressive and cause corrosion on copper pipes. The water can remove the protective film that forms inside copper. Our municipal water system treats the water with a sodium hydroxide to raise the pH (all per the EPA lead and copper rule)
Have your client get copy of the water suppliers consumer confidence report, call the supplier and discuss the corrosion.
A similar issue came up a few years ago, I asked our water quality manager, she googled the city, and found out they had a known issue with copper corrosion.

 

[don_resqcapt19]

I find this comment in the document that Brian linked to interesting.

... nor is it recommended that the piping system be used as the main electrical ground for a building or dwelling.

 

[hurk27]

My first test would be to take a voltage measurement between the service meter can and Earth, just push a long screw driver in the ground about 20' out in the yard, if you have more then 10 volts call the utility, not too common but happens where you have a lost or have a poor primary neutral connection.

I get told all the time that AC voltage on copper will not cause a problem, but in every case when I was called on a pipe pitting problem we had a voltage on the grounding that the above test will prove, if you have it at the meter can then it is ahead of this point, and will be on all that is bonded to this neutral after this point.

 

[suemarkp]

All of those points are good, but why would only one pipe of the 3 be affected? It also sounds like there is one water meter feed that then branches to 3 pipes to the house, so if it is corrosive water you'd think it would eat away at all 3 separate pipes?

Are all 3 water pipe systems (oh boy, better be careful about what a water system is) bonded together in the house? If only the center feed is bonded, perhaps there is excess current on the grounding system and bonding all 3 together will just deteriorate all 3 pipes instead of one.

I'd consider having the plumber make each of the 3 feeds non-metallic for a segment outside in the earth. Not sure how long the plastic needs to be -- perhaps only a foot or so.