WATER CHEMISTRY FOR SWIMMING POOLS

Chemicals used in Swimming Pools:
Proper water chemistry is essential to maintaining safe and consistent swimming pool operation. Chemicals used in swimming pools include: Disinfectants to destroy harmful or otherwise objectionable organisms; Alkalinity and pH Adjusters to maintain a consistent acid-base relationship and acid buffering capacity; Chlorine Stabilizer to prevent unnecessary loss of chlorine; Algicide to kill and prevent algae, and Filter Aids to help remove foreign material. Following is a discussion of various factors which affect water chemistry, how they affect swimming pools and how to use pool chemicals to restore a properly balanced water chemistry.

Total Alkalinity (TA)

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

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.

In some cases, soda ash can be used to raise total alkalinity. Pound for pound, soda ash raises alkalinity 60 percent more than sodium bicarbonate and is cheaper than sodium bicarbiante. The problem with using soda ash to increase alkalinity is it drastically increases pH. This can cause cloudy water and scale formation. 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.

Chart No. 4 – Raising Alkalinity Using Soda Ash

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.

Chemical manufactures are now marketing a total alkalinity increaser which combines the effects of sodium bicarbonate and soda ash. The product sodium sesquicarbonate or sodium hydrogen carbonate affects total alkalinity more than sodium bicarbonate, but does not cause quite as much increase in pH as soda ash does.

Chart No. 5 – Raising Alkalinity Using Sodium Sesquicarbonate

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 total Alkalinity – Total alkalinity can be lowered by adding muriatic acid or sodium bisulfate. 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.

Chart No. 6 – Lowering Alkalinity Using Muriatic Acid

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.

Chart No. 7 – Lowering Alkalinity Using Sodium Bisulfate

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.
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About Red Square Pools

Thank you for checking out our blog...we appreciate you taking the time to read our posts. To be quite honest, our posts come from your questions. Red Square Pool's wants to clear up the confusion and frustration of maintaining your pool and spa. We simply want to make Pool Maintenance and Repair SIMPLIFIED!! Let us know what your thinking by dropping us an email at info@redsquarepools.com. Have a safe and happy swimming experience!

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