Pool pump glossary

The words technicians use, explained simply.

Bearings

Ball bearings the motor shaft spins on. Worn, they squeal. Learn more →

Backwash

Reversing the flow through a sand filter to clean it.

Capacitor

Electrical part that helps the motor start. When it fails, the motor hums without starting.

Cavitation

Tiny bubbles forming and collapsing in the impeller when the pump is starved of water. Sounds like gravel. Learn more →

Decibel (dB)

Unit of sound level. A 10 dB drop sounds about half as loud. Learn more →

Impeller

Vaned wheel that pushes water through the pump.

Natural frequency

The rate at which an object on a soft support bounces on its own. Key to vibration isolation. Learn more →

O-ring

Rubber ring that seals the pump lid and fittings.

Priming

Filling the pump and suction line with water so it can pump. A pump that won't prime is pulling air. Learn more →

Resonance

Amplification of vibration when its frequency is close to a surface's or support's natural frequency. Learn more →

RPM

Revolutions per minute. About 3,450 RPM for a single-speed pump at full speed.

Shaft seal (mechanical seal)

Seal that keeps water from passing between pump and motor. Worn, it leaks and damages the bearings. Learn more →

Skimmer

Opening in the pool wall that draws surface water and catches debris in a basket.

Strainer basket

Basket at the front of the pump that catches debris before the impeller.

Suction side

The plumbing that brings water from the pool (skimmer, main drain) to the pump.

Transmitted vibration

Pump vibration that travels into the slab, deck, shed or pipes, often louder than the pump itself. Learn more →

Variable-speed pump

Pump with adjustable speed. Cheaper to run and quieter at low speed. Learn more →

Vibration isolation

Keeping a machine's vibration from passing into the surface it sits on, with a support designed for its weight and speed. Learn more →