In the pool circulation system, water leaves the pool through outlets to return to the pool pump. There are two types of pool outlets, and both are required for adequate circulation. The first is the surface skimmer, which is located along the pool wall on the surface; the second is the main drain, which is found at the deepest point in the pool. The main drain is also used to empty the pool when necessary.

Surface skimmers are one of the most important components of the circulation system. Most swimming pool contaminants (dirt, pollen, leaves, and oil) enter the pool on the water surface, and the surface skimmer is designed to pull debris from the surface before it has a chance to sink to the bottom. To ensure good surface skimming action, there should be one skimmer for every 500 square feet (46.5 sq. m.) of surface area. At least one skimmer should be placed on the downwind side of your pool.

Within the recessed box that makes up the skimmer is a basket that catches large debris such as leaves. This skimmer basket must be cleaned manually and checked daily to guarantee good skimming and filtering. Skimmers also have a regulating gate, or weir, that ensures good skimming action. Children must be prevented from playing with gates so that their hands or feet don't become trapped in them. Skimmers covers located on the deck must be nonslip. Skimmers with chemical feeders are available, as are float valves that can be placed in the skimmer and that automatically add water when the pool level is low.

On large public pools, gutters provide a continuous trough around the surface of the pool and produce outstanding surface skimming action.

The main drain outlet on the pool bottom also works to return water to the filters. When the pool bottom is littered with leaves or other debris, the valves can be adjusted to pull more water through the main drain to help clean the bottom. When brushing the pool, it is helpful to increase the suction from the main drain.

The main drain must have antivortex plates or covers in place to dissipate suction. The drain cover should be a tamperproof, corrosion-resistant grate in a color that contrasts with the bottom of the pool. The slots in the grates must not be wider than a half inch (12.7mm) to prevent entrapment. It is preferable that pools have more than one drain, and all drains should have antivortex plates.

Water Chemistry • Popular Disinfectants • Chorine • Calcium Hypochorite • Sodium Hypochlorite • Stabilized Chlorines •
Bromine • Other Disinfectants • Water Balance • pH • Total Alkalinity • Calcium Hardness • Total Dissolved Solids •
Balancing Pool Water • Water Testing • Pool Vacs & Sweepers •

Pool Maintenance • Daily Chores • Weekly Chores • Solving Common Problems • Cloudy, Milky Water • Malodorous, Irritating Water
Green Water • Red or Brown Water • Blue - Green Water • Blue or Black Water • Pump Problems • Sand in Pool •
Excessive Water Loss • Excessive Foaming