Free chlorine refers to both hypochlorous acid (HOCl) and the hypochlorite (OCl-) ion, or bleach, and is commonly added to water systems to sanitize, disinfect, and oxidize. When ammonia or organic nitrogen are introduced to the water through contaminants like sweat or organic materials, the chloramines known as monochloramine, dichloramine, and trichloramine will quickly form. Chloramines are also known as combined chlorine.
Total chlorine is the sum of free chlorine and combined chlorine. The level of total chlorine will always be higher than, or equal to, the level of free chlorine. If the total chlorine level exceeds the free chlorine level, a super chlorination or “shock” is needed. If the pool water has a strong, offensive odor and is irritating the skin or eyes of the swimmers, that may be a sign that you need to “shock” the pool to remove the total chlorine.
In short, free chlorine is chlorine that is available and ready to help keep your pool water clean. Combined chlorine has been “used up” and will no longer help with sanitizing your water. Total chlorine is the sum of both the free chlorine and the combined chlorine.
To decrease Free Chlorine you can partially drain and refill your water, but this will affect the rest of your pool parameters as well. Another method is to add sodium thiosulfate to lower the Free chlorine concentration. Lastly, Free chlorine levels will dissipate over time. If the water is covered you can expose it to sunlight which will speed up the degradation of the Free Chlorine.
You should test your pool or spa a minimum of 2-3 times per week. A spa should be tested before each use due to the higher water temperature and smaller water volume. Pool and spa testing is also advised after heavy swimmer use (i.e. a party), after animals have been in the pool, after a heavy rain, after fertilizing, etc. It is also advised to test your pool or spa 24-48 hours after chemicals have been added to ensure accuracy in rebalancing.
pH is the intensity of acid or alkaline materials in the water of your pool or spa.
Many things can cause pH levels to change including rainfall, dust, organic materials, covering your pool, or using various pool additives.
Total alkalinity measures the amount of alkaline substances (primarily bicarbonates and carbonates) in your water. Alkaline substances buffer your water against sudden changes in pH so that your water chemistry is more easily controlled.
Cyanuric acid (sometimes called stabilizer or conditioner) makes chlorine more stable in the sun’s UV rays, acting like a sunblock for your sanitizer by keeping it from degrading as quickly as it would otherwise. If the cyanuric acid is too low the chlorine levels can drop from an ideal range to zero in less than two hours. If cyanuric acid levels are too high, the chlorine will become less efficient. It is important to maintain cyanuric acid in the recommended range.
Total hardness refers to the amount of calcium or magnesium in your pool or spa water. When total hardness is too high scale can form causing pool filters or plumbing to clog and the water to appear cloudy. If water is too soft, or low in total hardness, it will become aggressive and slowly dissolve plaster walls and corrode metal fixtures. Swimming pools and spas should have a total hardness of 250-500ppm.
Algae are microscopic plants which can grow in your pool or spa. They obtain their nutrients from leaves, plants and other organic matter (including swimmers). Algae can be caused by one or more of the following: no available free chlorine, poor or inadequate filtration, poor circulation (leaving “dead zones” of stagnant water), elevated phosphates in the water, incorrect pH levels, too much cyanuric acid/stabilizer, or failing to test pool water regularly and adjust parameters.
The treatment of algae depends on the type present in the water (black, green or yellow). Most algae blooms can be addressed with algaecide and/or shock treatment. However, this does not effectively treat all algae. We suggest consulting with your pool or spa professional for treatment recommendations.