pH & Alkalinity
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Water Parameters for Ph and Total Alkalinity:

bulletpH - Ideal range is 7.4 to 7.6
bulletTotal Alkalinity - Ideal range is 80-100 ppm.

pH:

The pH is a measure of the active acidity in pool or spa water.  Technically it is a measure of the concentration of hydrogen ions in the water.  The greater the concentration of active hydrogen ions, the lower the pH.

On the pH scale from 0 to 14, 7.0 is neutral, less than 7.0 is acidic and above 7.0 is basic (or alkaline).  The range of acceptable pH level in a pool or spa is from 7.2 to 7.8, but the ideal range is 7.4 to 7.6.

When the pH approaches or goes below 7.2, the water becomes corrosive, damaging vinyl and plaster surfaces as well as pipes and other equipment.  Low pH can also result in eye irritation for the swimmer.

When the pH goes above 7.6, chlorine disinfectants are less effective in killing bacteria and algae.  The water can become cloudy and scale can form on the equipment, in sand filters and on the pool walls.  High pH can cause itchy skin and eye discomfort.

bulletWhen pH is too high, add acid - Acid combines with water, increases the hydrogen ion concentration, and lowers the pH.  Muriatic acid (dilute hydrochloric acid - 20 Baume) or Sodium Bisulfate (Dry Acid) are commonly used to lower the pH.  Always follow the label for instruction on adding acid.
bulletWhen pH is too low, add Sodium Carbonate (Soda Ash) - This is not the same as Sodium Bicarbonate (Baking Soda).  The carbonate ions from sodium carbonate combine with hydrogen ions to reduce the hydrogen ion concentration.  Sodium Carbonate is available in granular form.

Total Alkalinity:

Total Alkalinity is a measure of the "buffering capacity" of water, or its ability to resist a change in pH.

The ideal Total Alkalinity level for pool or spa water is 80 - 120 ppm.  When the Total Alkalinity is too low, the pH level can fluctuate widely and the water can become corrosive.  When the Total Alkalinity is too high, the pH will be high and scale will form on pool surfaces and equipment.

bulletTo lower Total Alkalinity, add Acid - The acid reacts with bicarbonates in the water and converts them, reducing the Total Alkalinity.  Add 1.6 pounds of Dry Acid (Sodium Bisulfate) per 10,000 gallons of water, or 1.3 quarts of Muriatic Acid, to decrease the Total Alkalinity by 10 ppm.  Retest and adjust the pH.
bulletTo raise Total Alkalinity, add Sodium Bicarbonate - This adds to the total bicarbonates in the water, raising the Total Alkalinity.  Add 1.5 lbs. Sodium Bicarbonate per 10,000 gallons of water to increase the Total Alkalinity by 10 ppm.

Remember, Total Alkalinity and pH level are closely related, so it is important to test pH after adjusting Total Alkalinity.  Likewise, a proper Total Alkalinity level is important in maintaining the recommended pH level.  It may take several sodium bicarbonate treatments to build the proper Total Alkalinity buffering level to keep the pH in the proper range.

To Increase Alkalinity using Sodium Bicarbonate

VOLUME OF WATER

Desired increase in ppm

400 Gallons 1000 Gallons 5000 Gallons 10,000 Gallons 20,000 Gallons 50,000 Gallons 100,000 Gallons
10 ppm 0.90 oz 2.24 oz 11.20 oz 1.40 lbs 2.80 lbs 7.00 lbs 14.0 lbs
20 ppm 1.79 oz 4.48 oz 1.40 lbs 2.80 lbs 5.60 lbs 14.0 lbs 28.0 lbs
30 ppm 2.69 oz 6.72 oz 2.10 lbs 4.20 lbs 8.41 lbs 21.0 lbs 42.0 lbs
40 ppm 3.59 oz 8.97 oz 2.80 lbs 5.60 lbs 11.2 lbs 28.0 lbs 56.0 lbs
50 ppm 4.48 oz 11.2 oz 3.50 lbs 7.00 lbs 14.0 lbs 35.0 lbs 70.0 lbs
60 ppm 5.38 oz 13.4 oz 4.20 lbs 8.41 lbs 16.8 lbs 42.0 lbs 84.1 lbs
70 ppm 6.28 oz 15.7 oz 4.90 lbs 9.81 lbs 19.6 lbs 49.0 lbs 98.1 lbs
80 ppm 7.17 oz 1.12 lbs 5.60 lbs 11.2 lbs 22.4 lbs 56.0 lbs 112.0 lbs
90 ppm 8.07 oz 1.26 lbs 6.30 lbs 12.6 lbs 25.2 lbs 63.0 lbs 126.0 lbs
100 ppm 8.97 oz 1.40 lbs 7.00 lbs 14.0 lbs 28.0 lbs 70.0 lbs 140.0lbs

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This website was last updated on
Tuesday May 24, 2011