The pump is the most important part of a swimming pool’s circulation system. When the pump isn’t working, nothing else does either.

Pump parts

Pool pumps consist of the same basic parts: the pump pot, pump basket, vacuum chamber (or volute), impeller and seal. They work in unison so the pump can generate suction. The pool water enters at the pump pot, which holds the pump basket and keeps a reserve of water that the pump needs to prime itself.

The water that enters the pump first must pass through the pump basket. The basket sits inside the pump pot and catches any debris that gets sucked in while vacuuming or from around the skimmer basket. It prevents the debris from clogging the impeller.

The pump action takes place in the vacuum chamber, which houses the impeller that moves the water. The impeller attaches to the motor and spins inside the vacuum chamber. The impeller will either be an open-faced, which has visible vanes, or a closed-faced model, which is plastic and has a cover over the vanes with an opening in the center to allow the water to enter. Last in line is the seal. The seal has an important job to do: Prevent water from leaking out of the vacuum chamber and air from leaking in. The seal must keep the water in the wet end of the pump so the dry side does not get damaged.

Now, how can water leak out from a vacuum chamber? Inside the pump, a vacuum is created at the eye of the impeller. Water is thrown out of the impeller creating velocity within the diffuser, which is converted to pressure. If the motor shaft seal is bad, this water under pressure will leak out through the seal.

Replacing the seal

Replacing a leaking seal is one of the first repairs a service technician learns. The following pictorials will provide a series of tips and tricks to make this repair easier and faster.

How a pump pumps

Swimming pool pumps use centrifugal force to move water through the circulation system.

“Centrifugal force” is defined as a force pulling an object outward as it rotates around a center. A good example of that is a looping roller coaster. The loops always turn into themselves; that way the riders are facing into the loop. As the roller coaster enters the loop, centrifugal force then pushes the riders (the object) away from the center of the loop and safely into their seats. The riders are actually at their safest when they turn upside down.A pool pump works the same way as the roller coaster. When water enters the middle (eye) of the spinning impeller, it is forced out through the impeller’s vanes. This action creates centrifugal force, an object moving away from the center. As the water is thrown out to the edges of the impeller, there is a reduction of pressure in the eye of the impeller. This creates a vacuum and draws more water into the impeller.