Swimming Pool Blog


Total Alkalinity in Swimming Pools


by Rob Cox, March 6, 2010

Total Alkalinity in Swimming Pools

total alkalinity in swimming pools

A close cousin of pH, the level of alkalinity in the water is a measurement of all carbonates, bicarbonates, hydroxides, and other alkaline substances found in the pool water.  pH is alkaline dependent; that is, alkalinity can be defined as the ability of the water to resist changes in pH.  Also known as the buffering capacity of the water, alkalinity keeps the pH from "bouncing" all over the place. 

Alkalinity or AT is a measure of the ability of your pool water to neutralize acids to the equivalence point of carbonate or bicarbonate. In swimming pools, the proper range for Total Alkalinity is between 80-120ppm (parts per million), but many find that higher levels of 150-180ppm may not pose a problem. Keeping your Total Alkalinity in proper range is important for proper pool water balance.

Having a Total Alkalinity level that is too low or too high can cause specific problems with your pool water chemistry, water clarity, pool surfaces and swimmer eye comfort.

 

When total alkalinity is too low:

  • pH will become erratic, bouncing high or low, even quickly after adjustment
  • Etching of pool plaster or corrosion of chrome pool equipment.
  • Corrosive water conditions can suck the plasticizers out of a vinyl liner.

When total alkalinity is too high:

  • pH becomes "locked" or difficult to adjust
  • Cloudy water and scale formation on pool equipment or inside of pool filters.
  • Decreased disinfectant efficacy, Chlorine doesn't work as well, leading to other problems.

 

Raising Alkalinity with Sodium Bicarbonate
Also known as Baking Soda, regular ol' Arm & Hammer can be effectively used to raise your pool water Total Alkalinity. Using "Bicarb" is a cost effective method, however, note that adding any "base" to the pool water will raise pH levels in addition to alkalinity levels in the pool. After adjustment of your Total Alkalinity, it may be necessary to lower the pH level.

  Raising Total Alkalinity in Pools Dosage Chart
Increase GALLONS - IN POOL
(ppm) 1,000 5,000 10,000 15,000 20,000 25,000 50,000
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.
60 0.84 lbs. 4.2 lbs. 8.4 lbs. 12.6 lbs. 16.8 lbs. 21.0 lbs. 42 lbs.
70 0.98 lbs. 4.9 lbs. 9.8 lbs. 14.7 lbs. 19.6 lbs. 24.5 lbs. 49 lbs.
80 1.12 lbs. 5.6 lbs. 11.2 lbs. 16.8 lbs. 22.4 lbs. 28.0 lbs. 56 lbs.
90 1.26 lbs. 6.3 lbs. 12.6 lbs. 18.9 lbs. 25.2 lbs. 31.5 lbs. 63 lbs.
100 1.40 lbs. 7.lbs. 14.0 lbs. 21.0 lbs. 28.0 lbs. 35.0 lbs. 70 lbs.

 

Raising Alkalinity with Soda Ash
Soda Ash is usually used to raise pH, but can also be used to raise total alkalinity. Soda ash raises alkalinity 50 percent more than sodium bicarbonate, but it also will raise pH strongly. This can create cloudy water and produce scale. Soda ash should only be used to increase total alkalinity if you also need to increase the pH or if only small increases in alkalinity are needed.

  Raising Total Alkalinity in Pools Dosage Chart
Increase GALLONS - IN POOL
(ppm) 1,000 5,000 10,000 15,000 20,000 25,000 50,000
10 0.09 lbs 0.44 lbs. 0.88 lbs. 1.32 lbs. 1.77 lbs. 2.21 lbs. 4.42 lbs.
20 0.18 lbs. 0.88 lbs. 1.77 lbs. 2.65 lbs. 3.53 lbs. 4.42 lbs. 8.83 lbs.
30 0.26 lbs. 1.32 lbs. 2.65 lbs. 3.97 lbs. 5.30 lbs. 6.62 lbs. 13.25 lbs.
40 0.35 lbs. 1.77 lbs. 3.53 lbs. 5.30 lbs. 7.07 lbs. 8.83 lbs. 17.66 lbs.
50 0.44 lbs. 2.21 lbs. 4.42 lbs. 6.62 lbs. 8.83 lbs. 11.04 lbs. 22.08 lbs.
60 0.53 lbs. 2.65 lbs. 5.30 lbs. 7.95 lbs. 10.60 lbs. 13.25 lbs. 26.49 lbs.
70 0.62 lbs. 3.09 lbs. 6.18 lbs. 9.27 lbs. 12.36 lbs. 15.46 lbs. 30.91 lbs.
80 0.71 lbs. 3.53 lbs. 7.07 lbs. 10.60 lbs. 14.13 lbs. 17.66 lbs. 35.33 lbs.
90 0.79 lbs. 3.97 lbs. 7.95 lbs. 11.92 lbs. 15.90 lbs. 19.87 lbs. 39.74 lbs.
100 0.88 lbs. 4.42 lbs. 8.83 lbs. 13.25 lbs. 17.66 lbs. 22.08 lbs. 44.16 lbs.

 

Raising Alkalinity with Sodium Sesquicarbonate
Chemical manufacturers are now selling a total alkalinity increaser which combines the effects of sodium bicarbonate and soda ash. Sodium sesquicarbonate raises total alkalinity more than sodium bicarbonate, but does not increase pH as much as soda ash does. More expensive than using Sodium Bicarbonate, but very specifically effective on Total Alkalinity in pool water.

  Raising Total Alkalinity in Pools Dosage Chart
Increase GALLONS - IN POOL
(ppm) 1,000 5,000 10,000 15,000 20,000 25,000 50,000
10 0.13 lbs. 0.63 lbs. 1.25 lbs. 1.88 lbs. 2.50 lbs. 3.13 lbs. 6.25 lbs.
20 0.25 lbs. 1.25 lbs. 2.50 lbs. 3.75 lbs. 5.00 lbs. 6.25 lbs. 12.50 lbs.
30 0.38 lbs. 1.88 lbs. 3.75 lbs. 5.63 lbs. 7.50 lbs. 9.38 lbs. 18.75 lbs.
40 0.50 lbs. 2.50 lbs. 5.00 lbs. 7.50 lbs. 10.00 lbs. 12.50 lbs. 25.00 lbs.
50 0.63 lbs. 3.13 lbs. 6.25 lbs. 9.38 lbs. 12.50 lbs. 15.63 lbs. 31.25 lbs.
60 0.75 lbs. 3.75 lbs. 7.50 lbs. 11.25 lbs. 15.00 lbs. 18.75 lbs. 37.50 lbs.
70 0.88 lbs. 4.38 lbs. 8.75 lbs. 13.13 lbs. 17.50 lbs. 21.88 lbs. 43.75 lbs.
80 1.00 lbs. 5.00 lbs. 10.00 lbs. 15.00 lbs. 20.00 lbs. 25.00 lbs. 50.00 lbs.
90 1.13 lbs. 5.63 lbs. 11.25 lbs. 16.88 lbs. 22.50 lbs. 28.13 lbs. 56.25 lbs.
100 1.25 lbs. 6.25 lbs. 12.50 lbs. 18.75 lbs. 25.00 lbs. 31.25 lbs. 62.50 lbs.

 

Lowering Alkalinity with Muriatic Acid
Total alkalinity can be lowered by adding muriatic acid. Acid may be added in doses of up to 1 quart per 10,000 gallons. Total alkalinity tests and further required additions of acid can be made every 2 hours. "Pooling" the acid in an area of low flow increases the hydrocarbon exchange and the effect to alkalinity levels than walking the acid around the pool, which will lower pH more.

  Lowering Total Alkalinity in Pools Dosage Chart
Decrease GALLONS - IN POOL
(ppm) 1,000 5,000 10,000 15,000 20,000 25,000 50,000
10 2.56 oz. 0.8 pts. 0.8 qts. 1.2 qts. 1.6 qts. 2.0 qts. 1 gal.
20 5.12 oz. 1.60 pts. 1.6 qts. 2.4 qts. 3.2 qts. 1.0 gal. 2 gal.
30 7.68 oz. 1.2 qts. 2.4 qts. 3.6 qts. 1.2 gal. 1.5 gal. 3 gal.
40 10.24 oz. 1.6 qts. 3.2 qts. 1.2 gal. 1.6 gal. 2.0 gal. 4 gal.
50 12.80 oz. 2.0 qts. 1.0 gal. 1.5 gal. 2.0 gal. 2.5 gal. 5 gal.
60 15.36 oz. 2.4 qts. 1.2 gal. 1.8 gal. 2.4 gal. 3.0 gal. 6 gal.
70 1.12 pts. 2.8 qts. 1.4 gal. 2.1 gal. 2.8 gal. 3.5 gal. 7 gal.
80 1.28 pts. 3.2 qts. 1.6 gal. 2.4 gal. 3.2 gal. 4.0 gal. 8 gal.
90 1.44 pts. 3.6 qts. 1.8 gal. 2.7 gal. 3.6 gal. 4.5 gal. 9 gal.
100 1.60 pts. 1.0 gal. 2.0 gal. 3.0 gal. 4.0 gal. 5.0 gal. 10 gal.

 

Lowering Alkalinity with Sodium Bisulfate
Total alkalinity can be lowered by adding sodium bisulfate, or granular acid. As with using liquid acid (muriatic), your pH will also be lowered, so it's best to use small doses, adding in specific areas of low circulation, instead of broadcasting across the water. 

  Lowering Total Alkalinity in Pools Dosage Chart
Decrease GALLONS - IN POOL
(ppm) 1,000 5,000 10,000 15,000 20,000 25,000 50,000
10 0.21 lbs. 1.06 lbs. 2.13 lbs. 3.19 lbs. 4.25 lbs. 5.31 lbs. 10.63 lbs.
20 0.43 lbs. 2.13 lbs. 4.25 lbs. 6.38 lbs. 8.50 lbs. 10.63 lbs. 21.25 lbs.
30 0.64 lbs. 3.19 lbs. 6.38 lbs. 9.56 lbs. 12.75 lbs. 15.94 lbs. 31.88 lbs.
40 0.85 lbs. 4.25 lbs. 8.50 lbs. 12.75 lbs. 17.00 lbs. 21.25 lbs. 42.50 lbs.
50 1.06 lbs. 5.31 lbs. 10.63 lbs. 15.94 lbs. 21.25 lbs. 26.56 lbs. 53.13 lbs.
60 1.28 lbs. 6.38 lbs. 12.75 lbs. 19.13 lbs. 26.56 lbs. 31.88 lbs. 63.75 lbs.
70 1.49 lbs. 7.44 lbs. 14.88 lbs. 22.31 lbs. 31.88 lbs. 37.19 lbs. 74.38 lbs.
80 1.70 lbs. 8.50 lbs. 17.00 lbs. 25.50 lbs. 37.19 lbs. 42.50 lbs. 85.00 lbs.
90 1.91 lbs. 9.56 lbs. 19.13 lbs. 28.69 lbs. 42.50 lbs. 47.81 lbs. 95.63 lbs.
100 2.13 lbs. 10.63 lbs. 21.25 lbs. 31.88 lbs. 42.50 lbs. 53.13 lbs. 106.3 lbs.