Correcting or Reducing Corrosion in Home and Commercial Piping Systems (Page 2)

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Technical Resources >> How-To-Guides >> Correcting or Reducing Corrosion in Home and Commercial Piping Systems (Page 2)

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Table 2. Saturation Index Calculation Chart (You can also use our Online Langlier Index Calculator)

Temp deg F = T	Calcium Hardness = H	Total Alkalinity = A
32° = 0.0	5 = 0.3	5 = 0.7
37° = 0.1	25 = 1.0	25 = 1.4
46° = 0.2	50 = 1.3	50 = 1.7
53° = 0.3	75 = 1.5	75 = 1.9
60° = 0.4	100 = 1.6	100 = 2.0
66° = 0.5	150 = 1.8	150 = 2.2
76° = 0.6	200 = 1.9	200 = 2.3
84° = 0.7	300 = 2.1	300 = 2.5
94° = 0.8	400 = 2.2	400 = 2.6
105° = 0.9	800 = 2.5	800 = 2.9
128° = 1.0	1000 = 2.0	1000 = 3.0

pH ___ + T ___ + H ___ + A ___ - 12.1 = Langlier Index

Example:
pH = 6.8 Temperature (“T”) = 53 Hardness = 75 ppm Alkalinity = 100

(6.8 + .3 + 1.5 + 2.0 ) – 12.1 = - 1.5 Langlier Index is - 1.5

If Index is less than -0.5 the water is Corrosive

If Index is between -0.5 and +0.5 the water is Balanced

If Index is greater than +0.5 the water is Scale Forming

Use the chart above (Table 2) to calculate the Saturation Index of your water, and then view the chart below (Table 3) to see where your water is on the Langlier Scale:

Table 3. Saturation Index and Recommendations

Saturation Index	Description	General Recommendations
-5	Severe Corrosion	Treatment Recommended
-4	Moderate/ Severe Corrosion	Treatment Recommended
-3	Moderate/Severe Corrosion	Treatment Recommended
-2	Moderate Corrosion	Treatment Should be Considered
-1	Mild Corrosion	Treatment Should be Considered
-0.5	Mild Corrosion/Near Balanced	Treatment Probably Not Needed
0	Balanced	Treatment Probably Not Needed
0.5	Near Balance	Treatment Probably Not Needed
1	Mild Scale Forming	Some Aesthetic Problems; Consider Treatment
2	Mild Scale Forming	Some Aesthetic Problems; Consider Treatment
3	Moderate Scale Forming	Treatment Should be Considered
4	Severe Scale Forming	Treatment Recommended
5	Severe Scale Forming	Treatment Recommended

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.

•	Calcite neutralizers raise pH, hardness and alkalinity.
•	Soda ash feeders raise pH and increase alkalinity but not hardness.


Typical calcite neutralizer. (Shown above, stainless steel tank on the stainless steel tank on the far right) installed in combination with an iron filter system and water softening system.		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.

The filters usually have an automatic backwash feature, where the calcium mineral media is periodically backwashed water. This keeps the media clean and also allows the filter to remove sediment from the water.

If there is also iron in the water, in some cases, you can use a Birm (a type of iron filter media) blend filter as a combination acid neutralizer and iron filter, all in one tank.

Under the right conditions there is little maintenance. Periodically, and depending on raw water pH and the amount of water used, additional mineral is easily added to the filter tank. This is typically once a year for the average home.

Properly sized, the system produces a very low-pressure drop at service flow rates, usually around five psi.

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.

Phosphate Feeders

Phosphate feeders contain crystals of sodium hexametaphosphate which allow addition of 1 to 5 ppm of phosphate into the water. This phosphate then coats the interior surfaces of the piping or plumbing, slowing down or arresting corrosion. In addition to the crystal by-pass feeder style, which uses a phosphate crystal encased in a filter cartridge canister, there are also liquid phosphate solutions available. Zinc-orthophosphate is commonly used by municipal water systems to correct aggressive or corrosive water conditions in their distribution systems.

In some cases, phosphate cartridge filters are used after neutralizers, water softeners or other treatment systems.

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