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| On private water systems, one of the most common causes
of corrosion is from low pH, which can be defined as acidic water
with a pH of less than 7.0 pH. Signs of acid water are corrosion of
fixtures, blue staining (from copper pipes) or rust staining (from
iron pipes). |
| 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.
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| Common causes for acidic water are acid rainfall due
to atmospheric carbon dioxide and other airborne pollutants, runoff
from mining spoils, and decomposition of plant materials. |
| Acidic waters can be high quality and are typically
low in buffering calcium minerals, but are high in dissolved carbon-dioxide
gas, which can cause the low pH or acidity. Treatment is accomplished
by neutralizing the water with the use of an automatic
neutralizer. These water 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.
Periodically, (once or twice a year for a typical residential application)
more mineral is added to the filter tank. |
| 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
very low, less than 5.0. Treating this type of water requires injection
of soda ash or sodium hydroxide with a metering
pump, and generally, the neutralizing type mineral filters described
above will not work well on this type of water. |
| If you have acid water (water less than 7.0 pH) and
you are on a private water system, such as a well or spring, and you
wish our technical staff to quote you a solution, it is important
to suppy us with an accurate water analysis. You can also contact
us so we can better assist you in recommending a solution. |
| Treatment Options: Calcite Media
Neutralizers & Soda-Ash Feeders |
| If the pH is low, or the water is low in alkalinity
or hardness, you can change the corrosive chemistry of the water by
raising the pH, increasing the alkalinity and/or increasing the calcium
hardness. |
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Calcite neutralizers raise pH, hardness and alkalinity. |
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Soda ash feeders raise pH and increase alkalinity
but not hardness. |
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| Typical calcite neutralizer. (Shown above, stainless
steel tank on the far right) installed in combination with an iron
filter system and water softening system. |
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Soda ash feeder. Yellow solution tank ( dimensions:24”
X 36”) with metering pump, shown installed near well head before
storage tank (storage tank not shown). |
| Calcite Neutralizers |
| One of the most convenient methods to raise pH, 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. |
| Soda Ash Feeders |
| Metering pumps are used to inject a small amount of
soda ash (sodium carbonate) into the water, usually in conjunction
with a contact tank. For best results, allow 10 minutes contact with
the water for pH adjustment to occur. |
| For home wells, when the metering pumps are 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 1 pound per 5 gallons of water),
a solution of between 50 and 500 ppm are injected, depending on the
pH, alkalinity and flow rate of the water. |
| Follow-up Testing for Quality
Assurance |
| The pH should be checked on-site and the metering pump
adjusted after the system is installed and running. Routine weekly
or monthly testing of the pH is recommended to make sure the treated
water has the desired pH level. |
| If the piping in the home is copper it is also important
to test for copper residuals to verify that the corrosion is slowing
down or has stopped. A simple copper test, done on the water that
is first drawn out of the tap will show if there is a copper residual
still in the water, indicating corrosion. Over a period of six to
twelve months the copper residual levels will slowly decrease in most
cases, after the water has been treated. |
| If the Corrosion Doesn’t
Stop: |
| In some cases the corrosion will continue even when
the pH is neutralized. This can occur if the existing piping is severely
corroded, or if there are other reasons or causes for the corrosion,
in addition to the acidic water. If there are dissimilar metals connecting
together, such as copper pipe and iron pipe joined together, corrosion
can continue to occur. Other causes include high levels of dissolved
oxygen, sulfate bacteria, high levels of dissolved solids and/or stray
electrical currents coming into contact with the water stream. |
| The cause must first be isolated before a solution can
be found, but if the water is acidic, the first step is to use an
acid neutralizer to raise the pH, and track the copper residuals in
the water, before using other solutions in combination with the neutralizer. |
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