Keeping your pool's pH in the correct range is a vital component of keeping your pool safe and sanitary. If the pH is outside of the range of 7.0 to 7.6, the chlorine cannot sanitize the water properly and kill any algae growth. Below are a few other effects of high or low pH levels.
When the pH is too high, calcium in the water combines with carbonates to form scales at the edges of the pool, trapping dust and dirt and eventually turning black. The water also becomes cloudy. Calcium carbonate clogs the sand in the filter, and the sand becomes similar to concrete. It then destroys the effectiveness of the filter.
You need 80 percent more chlorine to do the same work when the pH is too high because the chemical isn't as effective. It may also cause the eyes and nose to burn as well as causing dry and itchy skin.
On the other hand, when pH is too low, you might find another host of issues. For example, the water begins to dissolve the surface of the grout, plaster, or other material that makes up the bottom and walls of the pool. The surfaces become rough and makes a good home for algae. Metal corrodes, including ladders and rails in the pool and pipes and fittings in the filter. As the metal corrodes, sulfates form, which attack the walls of the pool and form brown or black stains. Chlorine activates and evaporates too fast to sanitize the water. You may also notice eyes and nose burn along with dry and itchy skin. Swimwear and pool toys fade, and the water damages other materials.
For optimal swimmer comfort as well as chlorine effectiveness, aim for a pH between 7.2 and 7.4. This is the natural range of pH for your eyes.