On private well water systems one of the most common causes of corrosion is acidic water. The pH scale is used to determine how acidic or alkaline a water chemistry is. Acidic water has a pH of less than 7.0. A pH of 6.0 to 6.5 is a common pH range found in wells with acidic water.
Signs of acid water are corrosion of pipes and fixtures, pinhole leaks in plumbing, and blue staining (from copper pipes) or rust staining (from iron pipes). Acidic water can also cause pinhole leaks and pipe failure over time. By raising the pH to the range of 7.0 to 7.5 the water can be made alkaline which will then reduce or eliminate pipe corrosion.
Corrosion is a natural process involving chemical or electrical degradation of metals in contact with water. The rate of corrosion will vary depending on the acidity of the water, its electrical conductivity, oxygen concentration, and temperature. Acidic water with pH values in the range of 6 to 7 is more corrosive to the metals used in plumbing systems than alkaline water. Both ground waters (wells) and surface waters (such as spring water or creeks) can be acidic.
Often these waters are great for drinking or household use, but are low in buffering calcium minerals, and contain dissolved carbon-dioxide gas, which can cause a low pH and acid condition. Without treatment, these waters can be contaminated with copper, lead and other metals from piping, fixtures and appliances, turning good water into contaminated drinking water.
When the water's pH is above 5.0, the most common way to neutralize the water is with the use of an automatic calcite neutralizing filter. These water filter tanks are filled with a blend of calcium and magnesium carbonates made from naturally occurring minerals. As water flows through these tanks, the mineral dissolves 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 iron.
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. Often the pH is less than 5.0. Treating this type of water requires using a soda ash feeder, and in some cases injection of sodium hydroxide.
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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.
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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. The contact tank allows the soda ash solution to thoroughly mix in the water and allows a few minutes for pH adjustment to occur. 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 water which creates a 10% solution), a feed of between 50 and 500 ppm is injected into the water supply. The exact amount depends 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 may be used, but in extreme cases where the pH is lower than 4 an injection of caustic soda (sodium hydroxide) may be required.
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Cut-away of copper pipe showing blue green corrosion
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Leaking water heater caused by acidic water. This house had copper piping and also suffered from pinhole leaks.
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Soda ash feeder
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