If the pool water was found to be pH 8.0, should an acid or base be added to return it back to normal (pH 7.2-7.6)? What type of double displacement reaction is this?

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.