Top 9 Causes of Copper Corrosion in Home Piping Systems

According to some estimates, copper corrosion costs the United States more than $1 billion a year.

Copper corrosion in home plumbing systems is a common phenomenon that can have many causes.

Besides actual piping failure, the telltale blue stains the oxidized copper leaves on sinks, tubs, and fixtures can identify copper corrosion.

Laundry and even blonde hair can often be tinted blue. Copper can be toxic, and water-containing levels over 1.0 mg/L should not be used for drinking.

If iron pipes are present, the water can be rusty or reddish and contain metallic or sulfur odors and sediment. Corrosion can cause the piping to fail, sometimes in less than 10 years!

What is Corrosion?

Corrosion is “the deterioration of a substance or its properties due to a reaction with its environment.” In plain words, the metal from the piping dissolves into the water as a result of various causes, causing pipe failure and corrosion of water heaters, appliances, and fixtures.

In plumbing systems, corrosion is due to physical and chemical reactions between the pipe material and water.

(If want to learn more about Copper Corrosion and water, check this post out.)

Top 9 Causes Of Copper Corrosion Problems

1. Low pH (acid water less than 7.0)

2. High pH (alkaline water greater than 8.5)

3. High levels of dissolved oxygen

4. High levels of salts dissolved in the water (total dissolved solids)

5. Corrosion-causing bacteria such as sulfate or iron bacteria

6. Electrochemical causes, such as improper grounding of electrical appliances to the copper piping, and/or lightning strikes through utility poles grounding wires

7. High velocity of water, relative to the size of piping, causing hydraulic wear on the piping, sometimes found in circulating hot water systems using pumps

8. Sand, sediment, or other grit in the water causing hydraulic wear on the piping

9. Improper installation of copper piping by failure to properly de-burr or ream the ends of the pipe and/or the use of excessive acid flux when soldering the pipes.

What Can Be Done to Stop Copper Corrosion in Homes

1. Identify the source and severity of the problem by inspecting the piping system and getting an accurate water analysis, especially if you are on well water.

2. Verify if unnecessary electrical appliances or wiring are connected to the piping and if the piping system is properly grounded to the earth. Verify that there is electrical continuity throughout the piping system. For instance, the copper piping should not be separated electrically by plastic water filters, sections of plastic pipe, plastic water softener bypass valves, etc. Install jumper cables around these items.

3. 

   Check for pH, hardness, alkalinity, temperature, and total dissolved solids, and calculate the LSI (Langelier Saturation Index) to determine whether the water is aggressive or corrosive.

4. Cut sections of the copper piping in half, inspect for the type of corrosion present, and look for signs of poor workmanship by the installers. If necessary, replace the copper pipe.

5. Install a calcite neutralizer tank or a soda ash feeder to raise the pH to 7.2 to 8.0, correct for low pH, and increase the water's alkalinity.

6. Set up a phosphate feeder before the copper piping. Phosphate can coat the piping and reduce corrosion effects by coating the interior surfaces of the piping with food-grade phosphate, causing an insulation surface to build up.

7. If total dissolved solids are high (over 1000 ppm), install a whole house reverse osmosis system, followed by a calcite neutralizer.

8. If your water has bacteria and/or sulfur odors, install a chlorinator or ozone system to disinfect it before it enters the home.

9. On City Water?  If your water is supplied to you by a municipal utility, then the first step is to call your water utility and report the problem. If this is an isolated case and none of your neighbors are having a corrosion problem, you should suspect that the cause is either improper grounding, stray currents, or improper installation of the copper pipe.  Get a good home test kit with copper tests so you can do your own testing at home.
10. On Well Water? If you take your water from a private well, the first task you should do is to get an accurate water analysis. The analysis should include pH, total hardness, alkalinity, total dissolved solids, iron, manganese, nitrate, chloride, sulfate, and copper. You should also measure temperature.

More ways to prevent corrosion

Plumbing engineers and system designers can significantly reduce pipe corrosion by making simple design adjustments.

1. Minimize velocity. Use larger diameter piping to keep velocities low:

Cold line velocity should be less than 8 feet per second

Hotlines should be less than 4 feet per second.

2. Minimize hot water temperature. In a circulating hot water system, make sure the return lines are the same diameter as the supply lines.

3. Avoid stagnant sections; minimize direction and size changes.

4. Specify low-corrosivity water-flushable fluxes

5. Avoid stagnant sections

6. Minimize direction and size changes

5. Prevent electrical currents by grounding directly to a copper rod driven into the earth. Do not attach a grounding wire to water pipes other than the main pipe ground. Route wires away from water pipes, and don’t use galvanized nails that touch copper piping.  CAUTION: This may need to be done by a qualified electrician.

6. Avoid induced stresses – provide enough pipe support and allow for thermal expansion.

7. Consider non-copper pipe (e.g., PEX or stainless steel) wherever its use is permitted.

8. Use non- or low-lead faucets, valves, and appurtenances. Use low-flow fixtures and appliances and aeration faucet outlets.

9.  Choose fluxes that meet ASTM B813 standards.

10. Specify that copper tubes and fittings be installed according to ASTM B828-92 standards
11. Emphasize careful reaming of the cut ends to reduce turbulence. Plumbing inspectors and the Copper Development Association both report that un-reamed tubing corrodes and fails much more quickly than tubing that is properly reamed.

12.  Use correct  ASTM B813 fluxes. Using excess flux or a corrosive flux causes early pipe failures.

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Best Plumbing Practices to Eliminate Copper Corrosion

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