VACUUM: Refers to the low pressure condition created in the suction line. Also refers to the cleaning process of sucking leaves, algae and debris from the pool floor.

VALVES: A device placed in the plumbing line which restricts or obstructs water flow to create desired hydraulics, or may permit flow in one direction only (as in a check valve).

Vermiculite: A natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed items. Vermiculite is formed by hydration of certain basaltic minerals.

VENTURI: Increasing water velocity by restricting pipe size usually accomplished by a spa jet.

VOLUTE: A volute is a curved funnel increasing in area to the discharge port. It is often used with impeller pumps. As the area of the cross-section increases, the volute reduces the speed of the liquid and increases the pressure of the liquid. One of the main purposes of a volute casing is to help balance the hydraulic pressure on the shaft of the pump. However, this occurs best at the manufacturer's recommended capacity. Running volute-style pumps at a lower capacity than the manufacturer recommends can put lateral stress on the shaft of the pump, increasing wear-and-tear on the seals and bearings, and on the shaft itself.

VISION SYSTEM: The technology which isolates nascent oxygen into a powerful sanitizing tool. See Cationic Sanitation.

VINYL LINER: One type of interior pool finish. The liner is draped over a sand or cementitious floor, and locked into the top of the pools wall.

WEIR: The device in a skimmer that controls the amount of water coming into the skimmer, and keeps debris inside. That "flapper-gate" thing.

ZAMBONI: What you needed during winter '96 to groom your backyard ice rink.