Letter 33598

Corrosion of copper pipes and high Cu values in domestic water system

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PROBLEM: Corroding pipes and copper precipitate in sink basins (and maybe in the bodies of my family as well).

I live in an old house, built in about 1940. All the pipes were galvanized, but I have been changing them to copper and have isolated the galvanized sections with dielectric unions. We are on a domestic well and our water has pH values that range between 6.1 and 6.9, depending on time of year. I’m not sure what is causing the pH change, but it seems that the lower pH values occur during the summer.

The pump intake is PVC. The piping between the pump and pressure tank is PVC. And, the outlet between the water conditioning tank and the main copper water pipes is PVC.

I installed a water conditioning system to manage the pH. The tank is filled with aluminum hydroxide and calcium carbonate. The water has become harder, but the pH doesn’t seem to be raised to normal (i.e., 6.9 to 7.1) as advertised. The thinking was (by the salesman, that is) that I had a low pH problem and that the copper was dissolving in this low pH environment. Measurements of pH in my well and on the downstream side of the pressure tank and water conditioner are about the same, suggesting that there may be electrolysis occurring further downstream somewhere.

The pipes are corroding on the inside. My plumber (who suggested that I contact an electrical or chemical engineer about this problem) said he rarely sees copper pipes that have become so "eaten away".

QUESTION: What can I do to stop the electrolysis and high copper concentrations in my drinking water?

1) Is there a non-toxic sacrificial metal that could be installed in the plumbing system?

2) Could I connect all plumbing components (pipes, hot water tank, well pump, recirculating pump, Jacuzzi pump, water conditioners, etc.) in the house with a copper wire and ground it to one of the electrical service grounding rods?

3) Is it possible that electrolysis is occurring because of the type of solder that was used in the copper pipes? Some of the copper pipes were installed long before I purchased the home. Is there a different electro-potential between copper and silver solder versus lead solder?

I need help and would sure appreciate any ideas and suggestions.

Bill Shiels
- Woodinville, WA, USA

I think your plumber's advice is basically good and that you need to contact an electrician or electrical engineer who is experienced in this. My presumption is that an electric current, possibly a ground loop, is causing this corrosion.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Another factor to consider could be microbiological action. This is normally characterized by separate nodules on the inside of the pipe. There are a number of organizations that can test for it. Check out MIC - microbially influenced corrosion. Good luck!

Karl Nitsch
- Toronto Ontario Canada

Domestic copper pitting occurs randomly with well water and only rarely on municipal water. Low pH, below 6.4 dissolves copper piping, generally through uniform wall loss and pipes last 5-10 years.The serious cause is carbon dioxide. The exact way of corroding is not readilly explainable with carbon dioxide.

Domestic well waters usually are treated with calcite mineral installed in a water softener tank. This method adds hardness to the water and elevates the pH. It is low maintenance and is used frequently. Another method is to install a soda ash liquid feed system and add as needed to get to 6.8-7.2 pH range.

More recently many pits are blamed on poor quality copper metal supplied from all over the world.

Best bet is to maintain clean pipes and neutralized water.

Galvanic corrosion protection is talked about in old farm houses where wiring may be questionable.

Angelo Baroni
- Downingtown, PA

My copper pipes are underneath my house, Katrinia flooded my house with 4 feet of water, should I change them.

SHANYE PETERS
SOCIAL WORKER - NEW ORLEANS, LA, U.S.A.

No, I don't think so. If they are exposed, you might rinse them with fresh water though. It is very common to use copper water pipes even for direct burial in the ground.

Ted Mooney finishing.com Brick, New Jersey

YES I AM A DO IT MY SELF PERSON AND I NEED TO INSTALL A NEW HOT WATER HEATER MY PIPES ARE COPPER AND I WAS WONDERING SO THAT IT WILL BE EASIER THAN USING A TORCH CAN I CHANGE THE ENDS OVER TO PVC

BARBARA MACKEY
HOBBYIST - LANCASTER, South Carolina

PVC is a nice material in many ways but has a very low temperature limit making it unacceptable for hot water piping in general, let alone connections right at the water heater. Get a handyman book on the subject of soldering copper pipes, Barbara; it's relatively easy. These days you can buy copper fittings with the solder already applied, and it makes it even easier. Good luck.

Ted Mooney finishing.com Brick, New Jersey