PLUMBING: Usually rigid or flexible PVC pipe (either 1 ½" or 2" in diameter) that connects all of the equipment in order to achieve circulation. Although you will likely never see the plumbing lines for your pool, these lines are the HIGHWAY that make circulation and filtration possible. Note: Some older pools used copper pipes or iron pipes to plumb (connect) the equipment.

MAIN DRAIN: Not used on every pool. If used, the main drain is typically installed in the deepest end of the pool. Along with the skimmer(s), the main drain is a component where circulation is initiated. The main drain is connected to plumbing that runs to the (suction side of the) pump. This allows the pump to draw water (as well as dirt and debris) from the bottom of the pool. The pump will then send the water to the filter, where the dirt and debris will be trapped and removed from the pool, and send only clean water back to the pool. The great majority of aboveground pools do not use a main drain.

SKIMMER: Some pools have one skimmer (especially aboveground pools), most pools have two skimmers, and some large pools have more than two skimmers. Skimmer(s) are installed through the wall of the pool, positioned half way under the surface of the water and half way above the water; in fact, the skimmer is used to judge the standard operating level of the water. Along with the main drain, the skimmer(s) are a component where circulation is initiated. The skimmer(s) are connected to the plumbing that runs to the (suction side of the) pump. This allows the pump to draw water (as well as dirt and debris) from the surface of the water. The water level, then, must ALWAYS be at least in the middle of the skimmer in order to deliver water to the pump. The pump will then send the water to the filter, where the dirt and debris will be trapped and removed form the pool, and send only clean water back to the pool. If leaves or other large debris are present, they will get caught in the SKIMMER BASKET(S).

RETURN JET: Few pools have one return jet (especially aboveground pools), while most pools have at least two return jets. Return jets are installed through the wall of the pool, usually positioned at least 10" below the surface of the water. Return jets are components where circulation is completed. Return jets are connected to the (discharge side of the) pump. Once the pump draws water out of the pool (via the main drain and skimmers), it is then forced through the filter (and perhaps a heater and an automatic chemical feeder), and finally sent back to the pool, via the return jets. Note: it is best to have the same size "eyeball" (opening) in each return jet to eliminate air bubbles and to allow for continuous and smooth water circulation