Water Testing Basics
What Conditions Should You Test?
For maximum protection of swimmers, as well as the fixtures and equipment, test the following regularly:
- Total alkalinity and pH: Total alkalinity measures the amount of alkaline substances in your water. These provide a buffer against sudden changes in pH, which is an index of the alkalinity or acidity of the water. A high pH level (too alkaline) can irritate the eyes and skin of swimmers, produce mineral scaling on the pool and equipment, and reduce the sanitizing action of chlorine. A low pH level (too acidic) can also cause swimmer discomfort as well as corrosion of pool fixtures and equipment.
- Chlorine: Chlorine is the most popular pool and spa disinfectant. Its purpose is to sanitize (kill all disease-causing organisms), disinfect (kill all living organisms) and oxidize (destroy ammonia, nitrogen-containing contaminants and swimmer waste).
Chlorinated pool water typically contains two forms of chorine: combined chlorine, which has used up its ability to disinfect; and free chlorine, which is still active and able to destroy bacteria, algae and other potentially harmful organic materials as they enter the water. The proper amount of free chlorine is important because it ensures ongoing, active protection for swimmers.
Interestingly, it is an over-abundance of combined chlorine — not an excess of active, free chlorine — which causes the eye irritation and the strong, sometimes offensive odor often associated with chlorine. Many people incorrectly assume this foul smell comes from an elevated level of free chlorine. Increasing free chlorine levels by adding a large dose of chlorine or a non-chlorine shock (a procedure called superchlorination or "shocking") can actually correct this condition.
Make sure your test kit tests for free chlorine — not just combined or total chlorine — because free chlorine is the best measure of protection for the bathers who use your pool or spa.
- Total hardness: The amount of calcium and magnesium in your pool or spa water is called total hardness. When total hardness is too high, scale can form, causing pool filters or plumbing to clog. The water may also appear cloudy. Water that is too soft will slowly dissolve plaster walls and corrode metal fixtures.
