What could the pool owner do to reduce the acidity of the pool?

Add a base

Explanation:

Two of the acids that may cause high pool acidity are hydrochloric acid (HCl) and hypochlorous acid (HOCl).

To reduce the acidity in the pool, they must add a base to neutralize the excess acid.

A commonly used base is sodium carbonate - Na₂CO₃ or washing soda. The equations for the reactions are:

Na₂CO₃ (aq) + 2HCl (aq) ⟶ 2NaCl (aq) + H₂CO₃ (aq)

Na₂CO₃ (aq) + 2HOCl (aq) ⟶ 2NaOCl (aq) + H₂CO₃ (aq)

The initially formed carbonic acid will decompose into carbon dioxide and water.

H₂CO₃ (aq) ⇌ CO₂ (aq) + H₂O (ℓ)