Pool, Spa + Wellness Glossary

Alkalinity

Total alkalinity is a measure of bicarbonate, carbonate, and hydroxide ions in pool water. Target range: 80 to 120 ppm. Acts as a pH buffer.

Anti-vortex drain

A pool main drain cover engineered to prevent suction entrapment. Required under the Virginia Graeme Baker Pool and Spa Safety Act (VGBA).

Backwash

The process of reversing flow through a sand or DE filter to flush trapped debris out to waste.

Balance

Pool water is balanced when pH (7.2-7.8), alkalinity (80-120 ppm), calcium hardness (200-400 ppm), and stabilizer (30-50 ppm) are all in range.

Bond beam

The reinforced concrete top edge of a gunite pool that supports the coping and tile line.

Bromine

Alternative sanitizer to chlorine. Common in indoor pools and spas. More stable at higher temperatures than chlorine.

CYA (cyanuric acid)

Pool stabilizer that protects free chlorine from UV degradation. Target: 30-50 ppm. Required outdoors, banned indoors.

Cartridge filter

Pleated polyester or paper filter element inside a tank. Cleaned by hosing off. Replaced every 3-5 years.

Chemical feeder

Device that automatically doses chlorine, bromine, or salt into pool water.

Chlorine generator

See: salt chlorine generator. Produces chlorine on demand from dissolved salt.

Coping

The cap stone or material at the top edge of the pool wall. Travertine, limestone, brick, or cast concrete most common.

DE filter

Diatomaceous earth filter. Highest filtration quality (down to 3 microns). Requires DE powder recharge after backwash.

Diving board

Spring board mounted at the deep end. Most municipal codes now require 8-foot minimum depth under the board.

Equipment pad

The concrete slab housing the pump, filter, heater, chlorinator, automation, and valving.

Fiberglass pool

One-piece pre-manufactured shell dropped into excavation. 1-3 week install.

Filter media

The filtering substance: cartridge (pleated), sand (silica), or DE (diatomaceous earth).

Free chlorine

The available, sanitizing chlorine in pool water. Target: 1-3 ppm.

Gunite

Sprayed concrete pool construction. Steel rebar + shotcrete + plaster finish. 8-14 week build.

Hardness

Calcium hardness. Target: 200-400 ppm. Low hardness corrodes plaster and metal; high hardness causes scaling.

Heat pump

Electric pool heater that pulls heat from ambient air. Most efficient in temperatures above 50 degrees.

Infinity edge

Pool that spills over one or more sides into a catch basin, creating the illusion of merging with the horizon.

Jandy

Pool equipment brand owned by Fluidra (Zodiac). Pumps, heaters, automation, salt systems.

Kreepy Krauly

Suction-side automatic pool cleaner. Made by Pentair.

Lap pool

Long narrow pool (typically 40-75 feet) designed for daily swimming.

LSI (Langelier Saturation Index)

Numerical scale predicting whether water is corrosive (negative) or scale-forming (positive). Target: -0.3 to +0.3.

Main drain

Bottom suction outlet. Required to meet VGBA anti-entrapment standards.

MAP-style cleaner

Microprocessor-controlled robotic pool cleaner.

Marcite

Traditional white pool plaster. 8-12 year lifespan.

Multi-port valve

6 or 7 position valve on top of a sand or DE filter (filter, backwash, rinse, waste, recirculate, closed).

Negative edge

See: infinity edge.

Ozone

Supplemental sanitizer. Ozone destroys chloramines and reduces chlorine demand.

pH

Acidity or alkalinity of pool water. Target: 7.2-7.8.

Pebble Tec

Premium exposed-aggregate pool finish. 20-25 year lifespan.

Pentair

Pool equipment brand. Pumps (IntelliFlo), heaters (MasterTemp), automation (IntelliCenter), salt (IntelliChlor), lights (IntelliBrite).

Perimeter overflow

Pool that spills over all four sides into slot drains. Highest-end pool style.

Plaster

Cement and marble dust finish applied over gunite. White plaster (marcite) is most common.

Pool cover

Mesh, solid, or automatic safety cover. Auto-covers run $14,000-$28,000 installed.

Pool light

Underwater niche-mounted color LED or single-color light. Most modern installs use Pentair IntelliBrite or Hayward ColorLogic.

Pop-up cleaner

In-floor cleaning system with rotating pop-up heads embedded in the pool floor.

Pump

Heart of the circulation system. Variable-speed (VS) pumps required on most new builds since 2021.

Quartzite finish

Quartz-enhanced plaster. Smoother than aggregate, harder than marcite.

Raised spa

Spa built above pool deck level with a spillway returning water to the pool. Most popular wellness integration.

Return jet

Wall fitting that returns filtered water to the pool. Typically 3-5 per pool.

Salt cell

Electrolytic plates inside a salt chlorine generator. Lifespan: 4-7 years.

Salt chlorine generator

Device that converts dissolved salt into chlorine via electrolysis. Pentair IntelliChlor, Hayward AquaRite, Jandy AquaPure are the dominant brands.

Sand filter

Filter using silica sand as the media. Requires backwashing weekly. Sand change every 5-7 years.

Shock

Adding a heavy dose of chlorine (typically 10x normal) to oxidize chloramines and kill algae.

Skimmer

Surface debris collector at the water line. Most pools have 1-2 skimmers.

Spillway

Stone, tile, or fiberglass channel that returns spa water to the pool.

Stabilizer

See: CYA. Cyanuric acid.

Sun shelf

Shallow (typically 9-12 inch) tanning ledge inside the pool for lounging.

TDS (total dissolved solids)

Sum of all dissolved minerals, salts, and chemicals. Target: under 1500 ppm fresh, under 4500 ppm salt.

Tile line

Decorative waterline tile that prevents staining at the air-water interface.

UV system

Ultraviolet light supplemental sanitizer that destroys chloramines and reduces chlorine demand.

Vacuum head

Manual pool vacuum that connects to the suction line.

Variable speed pump (VS)

Pool pump with electronically variable RPM. Required by federal DOE rule on most pumps since 2021.

Vinyl liner

Custom-cut vinyl sheet that lines a polymer or steel-wall pool. Replaced every 8-12 years.

Waterfall

Recirculating water feature that drops water from elevated weir into the pool.

Weir

The dam-like edge that creates a controlled waterfall flow.

Whirlpool

Older term for a hot tub or spa with circulation jets.

Zinc anode

Sacrificial anode bolted to the equipment pad to prevent galvanic corrosion of metal pool components.

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