pH – Definition

The pH is a measure of how acidic or basic the water is in the pool.  The pH scale is a
relative scale indicating that the water is more or less acidic.  The concept of pH balance is one which can be confusing, but it is actually fairly simple. 
Water can be either acidic (low pH) or basic (high pH) or balanced (neutral pH).

If the water is acidic, it means that the water has a pH that is lower than 7.0, which is
considered neutral.  Acidic water tends to corrode or etch things it comes in contact with.  Acidic water is generally “under-saturated” or
“hungry” meaning that it is seeking something to dissolve and combine with.  Examples of acidic materials include vinegar, orange juice, or
hydrochloric acid.

If the water is basic, it means that the water has a pH that is higher than 7.0, which is
considered neutral.  Basic water tends to deposit scale or carbonates on things it comes in contact with.  Basic water is generally
“over-saturated” meaning that it wants to deposit some of its excess material.  Examples of basic materials include baking soda, antacids and such.

If the water is balanced, it means that the water is not neither corrosive nor scale forming.  

The neutral point for pool water is a bit higher than the neutral point for water in general. 
This is because the pool generally has a basic environment (pool plaster, tile grout, etc) and a the water must be a bit more basic to accommodate it. We generally
accept 7.4 to 7.6 as a good pH point for pool water.  If you get any higher, then you risk scaling or cloudy water.  If you get lower then you risk
developing a corrosive environment.