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Electrical Grounding Pipe Corrosion

How To Stop Copper Pipe Corrosion With Electrical Grounding

Reid asks,
We have a new house that we chose to plumb with copper.   The service line from the well to the house is PVC.   The copper plumbing is properly bonded to the main electrical ground at the electrical panel.   The electrical ground is the rebar in the foundation.

We are working to eliminate all potential sources of corrosion in the plumbing since we are getting some traces of blue in our white sinks.  We have had the water pH and other chemistry tested and retested and it does not appear to be the source of the corrosion.

The water treatment people said to us “Your electrician is going to hate this, but they need to bond the plumbing to a separate grounding rod, not your electrical system.”   They were correct in as much as the electrician hates that idea and essentially won’t do it.

If the plumbing is properly bonded to the electrical system, which by all accounts it is, is there any electrical difference between bonding it to the electrical system or bonding it to a dedicated, separate grounding rod?   Would creating a separate stand-alone ground for the plumbing system possibly change the presence of a micro-voltage on the plumbing system?

Note: The senior supervisor at the electrician company spent time in the house, fixed an improperly grounded washer (or maybe it was the dryer) which was creating a small current on the ground.  After addressing the improperly grounded appliance, he asserted that there was zero voltage on the ground.   I tend to believe him, but we want to remove every possible source of corrosion in the piping that we can.

Can I stop copper pipe corrosion with electrical grounding?

Hi Reid,
Thank you for your question, it is our pleasure to be of assistance.

First of all, it is illegal and very dangerous to have a separate grounding system for your water pipe (or any other system) in your home.  Please see National Electrical Code (NEC) Articles 250.52(A)(1), 250.53(D), 250.68(C), and 250.104(A).

So, your electrician is correct.  Please consider the soldiers that died in Iraq from taking a shower.  They were killed because the water piping was not properly bonded to the main electrical grounding system.  I can get into the details as to why, but rest assured, your electrician is correct.

While we are not corrosion experts, grounding is a key component in reducing corrosion caused by galvanic action.  Voltages can only form where there is a resistance, so we bond to eliminate the difference in potential between the copper pipe and other conductive objects.

Now that said, your corrosion person is on to something in that we do not want stray currents on our copper pipe.  The NEC calls this objectionable current (NEC 250.6) and we want this fully eliminated.

Have your electrician use a clamp-on amperage meter to measure the current on the water pipe grounding electrode conductor (GEC), and onto the copper pipe itself (if the clamp will go around the pipe).

Also, have the electrician temporarily remove the water pipe GEC, and measure the resistance between the GEC and the water pipe.  It should measure very high resistance between the two.  Then have the electrician reinstall the mandatory bond.

If the results are that you have a very low current (only a few milliamps) and the resistance when the wire is removed is high, then your copper water pipe is bonded correctly, and electricity is NOT the cause of the blue stains (corrosion).

On the other hand, if you do have excessive currents, your electrician will need to trace the pipes to see how the currents are getting on the piping.  Remember, there could be currents in the water itself, which will present an interesting dilemma.  You will need to figure this out by measuring currents at the pump.  If you run into this problem, you will want to give us a call.

If the current is low, and the resistance is low between the GEC and the water pipe, this could simply mean that the pipe has been bonded to structural steel or some other conductive body, which could be perfectly ok.  However, there cannot be any other grounding conductors tied to the copper piping.  Do you know if your home is all wood construction?  Or do you have some steel?

I have a friend that is a water expert.  I contacted him about your issue and he stated “Low alkalinity will corrode the pipes out and the stains can be blueish green in color depending on the stages of corrosion and what gets left behind.  You are seeing cuprous oxide staining similar to what happens to a penny that gets battery acid on it”.

I hope this helps you out.  Good luck.
The Engineering Team at E&S Grounding Solutions

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