e. Factors Affecting pH.
Gaseous chlorine lowers pH drastically.
(2) Sodium and calcium hypochlorite tend to raise the pH moderately. Lithium
hypochlorite, cyanurates, bromine, and iodine have little effect on pH.
(3) Makeup water added to the pool may affect the pH, depending on the
pH of the new water.
(4) Windblown dust, debris, and contaminants brought in by bathers may
cause sudden changes in pH.
f. Control of pH.
Chemicals used to raise pH.
(a) Sodium carbonate (soda ash) and lime [Ca(OH)2] are the chemicals
most commonly used.
(b) Sodium hydroxide, though somewhat more dangerous to handle, is
often used to raise the pH in pools.
Sodium bicarbonate can raise the pH if the pH is low.
Chemicals used to lower pH.
(a) Sodium bisulfate is recommended as a safe and effective chemical
for lowering pH.
(b) Hydrochloric acid (muriatic acid) is commonly used, though
dangerous to handle.
Sulfuric acid (dilute) is used occasionally but is not recommended.
g. Figure. Figure 1-3 shows the pH scale and the effect of pH values on
swimming pool operations.