A swimming pool is a big container for water that is used for recreation such as swimming, floating or water sports. If it is an in-ground pool, then it is basically a big hole in the ground. If it is above ground, then it is typically a large bowl. To keep the water clean and safe for swimming, the pool uses both chemical and mechanical mechanisms. Chemical processes may include chlorine or other chemicals that kill germs, and the mechanical mechanisms include a pool pump, a filter and a skimmer. The skimmer is typically located at the water line of a swimming pool. It filters out the largest debris from the pool--such as leaves and bugs--before they can become saturated and sink to the bottom of the pool. This prevents the debris from being pulled into and clogging the filter.
The filtering system of an above-ground pool is slightly more simplistic than that of an in-ground pool. For an above-ground pool, the pool skimmer is located at the mouth of the pool pump's intake valve, which is attached to the upper side of the pool through the pool's wall. The pool pump takes water in through the skimmer, and the skimmer filters out the debris through a basket as the water moves into the pool filter. Typically the pool's maintainer can open the skimmer from the outside to clean out the skimmer's basket. The water is returned to the pool once it has been filtered through a return port. Smaller pools typically only have one skimmer, pump, filter and return port.
The mechanism for the skimmer is typically separate from the pool's filter in an in-ground pool, and there may be more than one skimmer located around the perimeter of an in-ground pool, depending on the size of the pool. For an in-ground pool, the pool's intake valve is located in the bottom of the pool. The skimmers draw in water in the same way as the main drains, by sucking in water; however, unlike the drains, the skimmers only draw in water from the top layer of the pool. Most in-ground pool skimmers are buried in the ground just behind the wall of the pool. They will have an access hatch located in the pool's decking for easy access. Water flow into the strainer's intake valve is controlled by a floating door, known as a weir. The water flows through a strainer basket, which catches the largest debris. The skimmer will also have a secondary line that will equalize the water level in the skimmer if the water ever runs below the level of the intake valve. This prevents the skimmer from taking in air if the water level of the pool drops below the intake valve. The water is returned to the pool through a return port.