Think of a pool skimmer in a residential swimming pool like you would a gutter in a larger public swimming pool: it helps to clean by skimming water and capturing floating debris such as leaves, flower petals, dirt, twigs, dead insects, and oil (sunblock)― before the waste can sink to the pool’s bottom.
Most skimmers on in-ground pools are built into its upper sides, where the suction draws debris and traps it. Most pool skimmers are accessed via the pool deck area through a trap door or hatch. The skimmer is also in a convenient location to attach a suction line for a pool vacuum.
A surface skimmer is typically made of plastic (or PVC) or precast concrete and has a tank with a projecting throat on its upper side. The skimming action is performed by the weir, which regulates the amount of water entering the skimmer. Since the weird adjusts to permit only a thin layer of water to spill over, water is pulled off the surface quickly―keeping a large part of the pool surface clear.
One skimmer that is positioned in a good location can keep about 500 square feet of its surface clean. If the debris gathered by the skimmer is left to accumulate, it can put additional strain on the pump. For this reason, among others, the skimmer basket should be cleaned out daily during swim season.
A skimmer must be installed with an equalizer line, which is a pipe that connects from the bottom of the skimmer basket through the pool wall and into the water. The equalizer helps to prevent air from being sucked into the system if evaporation causes the water level to drop below the weir level. Make sure air doesn’t enter the system―it could cause the pump to stall.
Many pool skimmers come equipped with automatic water level controls and automatic chlorinators.