Swimming pool owners have one main goal when it comes to their pools: achieving sanitary water that's crystal-clear and sparkling. A swimming pool's water sanitation is handled by disinfection, including through chlorination or by other methods. Crystal-clear and sparkling pool water, in part, is also made possible by good disinfection, but it's also improved on occasion by clarification. For example, there are times when a swimming pool's water becomes cloudy-looking, and that's when a clarifier such as a flocculant, or flock, will help.
Flocculation is used in water purification to remove fine particulate matter suspended in the water. In swimming pools, a flocculant, or flock, is a substance that causes fine particles in its water to aggregate or come together. Fine particulate matter in water that comes together is known as "floc." Many pool clarifiers make use of flocculation to clear up cloudy pool water. Pool flock is especially useful when fine particulate matter is in the water and it's too small to filter out.
Typically, pool water clarifiers such as flocks are needed when swimming pool water is cloudy, yet chemical levels are correct and filtration units are working fine. Often, fine particulate matter that leads to cloudy pool water ends up in a pool after heavy winds and rain. Also, fine particulate matter can be left in a swimming pool after it's been shocked. Shocking a pool to kill algae or other organic matter will leave behind dead algae and other dead particulate matter that escapes filtration.
After a swimming pool flock has been applied to the water, the fine particulate matter in the pool will come together as floc. Pool floc that's large will sink to the swimming pool's bottom so you can vacuum it up. Some pool floc, though, won't be large enough to sink, and it'll end up in the pool's filtration unit. Floc that ends up in a pool's filtration unit can cause clogging, but backwashing, or reversing, the filter as needed should address that issue.
There are both natural and synthetic swimming pool flocks on the market. For ease of use, select a pool flock that doesn't affect a swimming pool's pH balance. The typical dose of flock needed to address a pool's cloudy water is approximately 227gr. in a 10,000-gallon pool. After adding pool flock, let the swimming pool's filter run for about two hours, and then shut it off for 12 to 24 hours. Vacuum up any flocculated matter that's settled to the pool's bottom.