How Does a Swimming Pool Pump Work?

The Pump

The average swimming pool pump is known as a self-priming centrifugal pump, meaning the pump houses a vacuum chamber that must be full of water in order for the vacuum to have effect. Hence, the pump yanks water from the pool in order to operate properly.
Self-priming occurs thanks to the motor and a pump diffuser. The motor drives the pump impeller, the tips of which are securely contained within the pump diffuser. The impeller converts water velocity into water pressure at a rate that is unique to the horsepower of the pump's motor.
There are two kinds of pump diffusers: those that are molded into the pump's cover and those that have an altogether separate diffuser. Irrespective of type, the diffuser keeps air from infiltrating the pump housing. When air is actively being removed, bubbles will return to the pool as an indicator of the pump operating correctly.

Water Filtration

Before the water enters the pump, it passes through a metal strainer basket that acts as a filter for leaves, sticks and various debris. At this point, the water enters a filter system. There are a few kinds of filter systems, the first of which is a sand filter system in which dirty pool water enters an inlet pipe. This pipe channels the water to the tank's water distribution head where the filtering truly takes place. The sand particles in the tank act as a filtering mechanism. The water is pulled through the sand, and the sand catches the debris, thus purifying the water. The water is then shot through the outlet pipe and back out.
Some pool systems instead opt for a cartridge filter or diatomaceous earth filter. In the latter, water moves through filter grids coated with diatomaceous earth, which is a fine powder made from dead sea organisms. This powder acts as the filter. In a cartridge filter, water flows through a paper or cloth veil that acts to purify the water.

Pump Management

There are only a few variables to remember when considering the care of your pool pump. The pump should be kept free of dirt and debris, and guarded against rainwater flooding, as the motor can be adversely affected. Additionally, while water must be moved from the pool to the pump, any air infiltration resulting from this process could damage the pump.
At times, it will be necessary for a pool's sand filter to be backwashed, as the debris caught by the filter can eventually slow water flow. Pressure gauges will indicate whether a backwash is necessary. If there is more pressure measured in the inlet pipe than the outlet pipe, a backwash by a pool caretaker will have to be performed. With a cartridge filter, removing the cloth piece and washing it out will do the trick.