You're right to be skeptical. While electrolysis of copper pipes can occur, it's typically from stray DC current, and it's relatively rare. The sudden increase in occurrences you're seeing is suspicious. Here's a breakdown of the issue and things to consider

Understanding the Chemistry & Potential Causes
Electrolysis and Copper Pipes

Electrolysis happens when a DC (direct current) flows through water, causing copper to dissolve from the anode (positive electrode) and deposit elsewhere. The dissolved copper can cause staining and the green/blue discoloration you describe.

Stray DC Current Sources

This is the key! Where's the DC coming from? Here are possible, though less likely, sources:

Faulty Grounding

Improper grounding of electrical systems can lead to stray currents finding paths through plumbing.

DC Transit Systems

If the homes are near a DC-powered rail system (subway, light rail), stray currents could be leaking into the ground and finding their way to the plumbing. This is more common in older systems with poor insulation.

Welding

Improperly grounded welding equipment can also create stray currents.

High-Voltage Transmission Lines

Proximity to high-voltage DC transmission lines could, in theory, induce currents in nearby buried metal.

Low Voltage Landscape Lighting (if improperly wired)

Even though the voltage is low, poor wiring or transformer issues could introduce DC current.

Why DC and Not AC? AC (alternating current) doesn't cause significant electrolysis. The alternating flow of electrons cancels out the dissolving effect. Confirmation of Copper Leaching

You can test for copper in the water using a water testing kit or sending samples to a lab. Document the results.

Here's what I recommend you do to investigate the copper leaching and any suspected stray current


Thorough Electrical Inspection



Grounding System

Verify the grounding system of the home. Check the ground wire connections, ground rods, and bonding of metal pipes to the electrical system. A loose or corroded ground connection is a prime suspect.

Appliance Leakage Current

Use a clamp meter to check for leakage current on appliance ground wires. (Refrigerators, washing machines, etc.). Unplug appliances one at a time to see if the current drops.

Neutral-Ground Voltage

Measure the voltage between the neutral and ground wires at various outlets. A significant voltage (more than a few volts) indicates a problem.2.

Test for Stray DC Current on Pipes



Multimeter

Set your multimeter to DC volts. Connect one lead to a known good ground (like the electrical panel's ground bus) and the other to the copper water pipe. Measure the voltage. Anything more than a very small fraction of a volt (millivolts) warrants further investigation. Move the probe to different sections of pipe, including where they enter and exit the house.

Pipe-to-Soil Voltage

Drive a copper ground rod into the earth at least 3ft away from the pipe and use a multimeter to test the voltage between the water pipe and ground rod. This can give an indication of voltage gradients in the soil.3.

Check with Neighbors

Ask neighbors if they are experiencing similar issues with their water. This could indicate a wider problem with the area's grounding or a common source of stray current.4.

Water Quality Test

A comprehensive water test will determine the copper levels and other contaminants present. This will provide a baseline for future comparisons.5.

Contact the Water Utility

Inquire with the local water utility about the water quality in the area. They may be aware of elevated copper levels or other issues.6.

Look at the History

What type of pipe system does the home have? Galvanized, copper, or pex? Is there a water softener installed? Is the home on a well?

Important Considerations and what to do if you find stray current on a water pipe



Licensed Electrician

Do not attempt any electrical work yourself if you are not a qualified and licensed electrician. Stray current issues can be dangerous.

Document Everything

Keep detailed records of your inspections, measurements, and communications with customers.

Grounding and Bonding



Water Meter

Make sure the water meter is properly bonded.

Proper Bonding

All metal pipes should be properly bonded to the electrical grounding system.

Additional Thoughts Water Softeners

Water softeners can sometimes exacerbate copper leaching by increasing the water's conductivity.

"Water Control Company"

Be wary of companies making exaggerated claims. It's possible they are trying to sell expensive water treatment systems. Always get a second opinion from a reputable source.

Coincidence

It is possible that these incidents are coincidental. There could be other factors affecting water quality in these homes.

In summary: While electrical current can* cause copper leaching, it's not a common occurrence. Thoroughly investigate the grounding system, test for stray current, and gather as much information as possible before jumping to conclusions. Involve a qualified electrician to diagnose and correct any electrical problems. Do not try and fix the issues if you're not qualified. Flag for review