Different sources of chlorine have different effects on pH:
• Chlorine gas decreases pH
• Sodium hypochlorite increases pH
• Calcium hypochlorite increases pH slightly.
It may be necessary to add a common acid (like vinegar) to lower the pH. Small amounts
of sodium hydroxide (lye) may be used to raise the pH. Inexpensive test papers for
checking both the chlorine level and pH may be obtained from most swimming pool and
chemical supply houses.