How To Treat Copper Pipe Corrosion

According to some estimates, corrosion costs the United States more than $1 billion a year. Copper corrosion in home plumbing systems is a common phenomenon, which 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.

Often laundry and even blonde hair can be tinted blue. Copper can be toxic, and water-containing levels over 1.0 mg/L should not be used for drinking. If there are iron pipes present, the water can be colored rust or reddish, and contains metallic or sulfur odors, and sediment.Eventually corrosion can cause the piping to fail, in some cases 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. Corrosion in plumbing systems is due to physical and chemical reactions between the pipe material and water.

The main causes of pipe corrosion are:

  • • Low pH (acid water) typically found on private well water, but is also present in some small municipal water systems.
  • • Other water chemistry causes, such as high levels of dissolved oxygen, high levels of salts dissolved in the water, and/ or corrosion-causing bacteria such as sulfate or iron bacteria.
  • • Electrochemical causes, such as improper grounding of electrical appliances to the copper piping.
  • • High velocity of water, relative to size of piping, causing hydraulic wear on the piping, for instance a recirculating hot water system with a pump driving the water through pipes that are too small in diameter.
  • • Poor plumbing installation practices, including not cleaning or de-burring the pipe properly and the use of excessive flux in soldereing the pipe fittings.
  • • Sand, sediment or other grit causing hydraulic wear on the piping.
  • • Lightening strikes to utility poles where the electricity travels to ground wires connecting to piping systems

What can be done?

  • 1)Identify the source and severity of the problem by inspection of the piping system and water analysis:
    • • Check to see if there are unnecessary electrical appliances or wiring connected to the piping.
    • • Check to see if the piping system properly grounded. Verify to see that there is electrical continuity through out the piping system.
    • • Check for pH and see if the water is corrosive, and/or perform a Langlier Index (see Table 2)
  • 2)Correct or minimize the cause of the corrosion above.
  • 3) Install a calcite neutralizer tank, or a soda ash feeder to raise the pH to 7.0 to 8.0 to correct for low pH and increase the alkalinity in the water.
  • 4) Install a phosphate feeder before the copper piping. Phosphate will coat the piping and reduce or slow down the corrosion effects, by coating the interior surfaces of the piping with phosphate and causing an insulation surface to be built up.
  • 5) Check to see if there are unnecessary electrical appliances or wiring connected to the piping.Check to see if the piping system properly grounded.Verify to see that there is electrical continuity through out the piping system.Check for pH and see if the water is corrosive, and/or perform a Langlier Index (see Table 2 in the next page, or you can use our Online Langlier Index Calculator).

Calcite Neutralizer Filters

One of the most convenient methods to raise pH, and add a little hardness and alkalinity is to use a calcite neutralizer filter. These filters will typically raise the pH of the water to 7.0 to 8.0 and add 30 to 100 ppm of hardness depending on the alkalinity and water hardness.

In neutralizer filters, acidic waters slowly dissolve the calcium and magnesium media on contact as the water flows through the filter, raising the pH of the water and increasing the alkalinity. This eliminates the effects of corrosive water chemistries and can help to prevent corrosion of piping and fixtures.

The size of the system is directly proportional to the flow rate of the water, in gallons per minute. The higher the flow rate, the larger the system required.

Neutralizer filter tanks are filled with a blend of calcium and magnesium carbonates made from naturally occurring minerals, which dissolve into the water, making it less corrosive. More mineral can quickly and easily be added to the filter tank, typically once per year for most residential applications. No special tools are required.

This type of neutralizer also acts as a filter removing sediment and small amounts of rust from the water, and then backwashing it out once every week or so.

Soda Ash Feeders

A small pump called a metering pump is used to inject a small amount of soda ash (sodium carbonate) into the water, usually in combination with a contact tank. For best results, allow a few minutes of contact with the water for pH adjustment to occur and the soda ash solution to thoroughly mix in the water by using a contact tank. For home wells the metering pumps are usually wired to turn on and start pumping soda ash solution when the well pump is energized or running.

Soda ash is bought dry, usually in 25 or 50 lb bags and mixed with soft or pure water in the solution tank. When a saturated solution is achieved (approximately 3 pounds per 5 gallons of wate, which creates a 10% solutionr), a solution of between 50 and 500 ppm are injected, depending on the pH, alkalinity and flow rate of the water.

In some cases, instead of dissolved carbon dioxide causing the low pH or acidity, the acidity is caused by mineral acids, either natural or from mining or other industrial wastes. In this type of water, tthe pH is less than 5.0. A soda ash feed pump is used, or in some cases injection of sodium hydroxide is required.

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Cut-away of copper pipe showing blue green corrosion.

Leaking water heater caused by acidic water. This house had copper piping and also suffered from pinhole leaks.

Pipe corrosion in cold water pipe caused by the use of excessive flux during installation.

Calcite Acid Neutralizer Filter

Soda Ash Feeder

  • Clean Water Systems & Stores, Inc., Water Treatment Equipment,Service & Supplies, Santa Cruz, CA