Final answer:
To increase the pH level of swimming pool water, soda ash (sodium carbonate) should be added. It works by reducing the hydrogen ions in the water which causes the pH to rise.
Step-by-step explanation:
To raise the pH of swimming pool water, one can add soda ash (sodium carbonate). When dissolved in water, soda ash increases the pH by hifting the bicarbonate/carbonate equilibrium which typically causes a reduction in hydrogen ions (H+) in the water, resulting in a higher pH level. This contrasts with other chemicals like bromine, sodium chloride, or muriatic acid, which have different roles in pool maintenance. Bromine and sodium chloride are more commonly associated with sanitization, whereas muriatic acid is actually used to lower pH levels due to its acidity.