Total alkalinity is closely associated with pH but rather than a measure of hydrogen ion concentration it is a measure of the ability of a solution to neutralize hydrogen ions. Expressed in parts per million (ppm), total alkalinity is the result of alkaline materials including carbonates, bicarbonates and hydroxides - mostly bicarbonates. This acid neutralizing (buffering) capacity of water is desirable because it helps prevent wide variations in pH whenever small amounts of acid or alkali are added to the pool. Total alkalinity is a measure of water's resistance to change in pH.
Total alkalinity should be maintained in the range of 80 to 150 ppm.
If total alkalinity is too low:
pH changes rapidly when chemicals or impurities enter the water. pH may drop rapidly, causing etching and corrosion.
If total alkalinity is too high:
pH becomes difficult to adjust. High pH often occurs causing other problems such as; cloudy water, decreased disinfectant effectiveness, scale formation and filter problems.
Raising total Alkalinity - Total alkalinity can be raised by the addition of bicarbonate of soda (sodium bicarbonate, baking soda). 1.4 lbs. bicarbonate of soda per 10,000 gallons will raise total alkalinity 10 ppm.
Chart No. 3 - Raising Alkalinity Using Sodium Bicarbonate
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Increase
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GALLONS IN POOL
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|
(ppm)
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1,000
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5,000
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10,000
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15,000
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20,000
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25,000
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50,000
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|
10
|
0.14 lbs
|
0.7 lbs.
|
1.4 lbs.
|
2.1 lbs.
|
2.8 lbs.
|
3.5 lbs.
|
7 lbs.
|
|
20
|
0.28 lbs.
|
1.4 lbs.
|
2.8 lbs.
|
4.2 lbs.
|
5.6 lbs.
|
7.0 lbs.
|
14 lbs.
|
|
30
|
0.42 lbs.
|
2.1 lbs.
|
4.2 lbs.
|
6.3 lbs.
|
8.4 lbs.
|
10.5 lbs.
|
21 lbs.
|
|
40
|
0.56 lbs.
|
2.8 lbs.
|
5.6 lbs.
|
8.4 lbs.
|
11.2 lbs.
|
14.0 lbs.
|
28 lbs.
|
|
50
|
0.70 lbs.
|
3.5 lbs.
|
7 lbs.
|
10.5 lbs
|
14.0 lbs.
|
17.5 lbs.
|
35 lbs.
|