A swimming pool is basically an enclosed body of water, which means it comes with certain conditions; one of them is its pH. The pH of swimming pool water, or any water, is simply a measure of how acidic or alkaline that water is. A swimming pool with a pH below 7 is said to be in an acidic state. When swimming pool pH declines too far below 7, its water can become too acidic and even dangerous to swim in.
Water itself, all things being equal, has a neutral pH of 7. However, the recommended pH for a swimming pool should be between 7 and 8, with a pH of 7.4 to 7.6 being highly desirable. Once a pool's pH begins dipping below 7, meaning its acidity intensity is increasing, swimmers begin experiencing issues like eye and mucus membrane irritation. Like acid rain, a swimming pool's acidic pH level is corrosive to both swimmers and pool equipment.
A pH level of 0 in a swimming pool would mean the water itself is a strong acid and therefore mortally dangerous. However, it would take a cataclysmic event to give a pool a pH of 0. Dumping thousands of gallons of acid into a swimming pool, for example, would cause its pH to decline to dangerous levels. What's more dangerous in pools with pH levels below 7 is that chlorine will completely disappear, raising the risk of potentially deadly bacterial contamination.
Common types of vinegar range in pH from 2.4 to 3.4, and there's no serious safety risk when a liquid of that pH is splashed on a person. Vinegar or other food-type liquids with pH levels between 2.4 and 3.4 are often used as medicinals. However, any pool pH level below 7 will negatively affect swimmer comfort, for starters. As pool pH declines below 6, for example, eye irritation would start to become severe or even hazardous.
When swimming pool pH rises to about 7.8, an acid is added to the water to lower its pH. The most common acid used to lower pool pH is muriatic acid, which should be used in strict accordance with instructions. Allowing swimming when a pool's pH goes below 6.7 will make it too acidic for comfort. To raise pool pH back above 7, just use 1.5 lbs. of sodium carbonate per 20,000 gallons of water.