A base such as Sodium Bicarbonate (Baking Soda), added to your pool, will increase alkalinity which increases the buffering capacity of the pool; your pool's resistance to pH change.
The ability of the pool to resist changes in pH, which prevents water balance. The buffering capacity is given by the alkalinity, a close cousin to pH. If your pH bounces, or resumes previous levels soon after adjustment, your buffering capacity is too low. Check your total alkalinity.