Pool operations glossary

AFO (Aquatic Facility Operator)

An alternative to CPO certification, administered by the National Recreation and Park Association (NRPA). Satisfies the same Illinois IDPH operator requirement.

CPO (Certified Pool/Spa Operator)

An industry-standard certification issued by the Pool & Hot Tub Alliance (PHTA) for the licensed operation of commercial and semi-public pools. Required by Illinois IDPH for every semi-public aquatic facility.

StarGuard Elite

A commercial lifeguard certification program administered by StarGuard ELITE / Jeff Ellis Management Inc. Widely accepted by Illinois IDPH for semi-public aquatic facilities.

Pool Turnover Rate

The time required for the entire pool volume to pass through the filtration system once. Illinois IDPH sets maximum turnover times by facility type.

Saltwater Chlorine Generator (SWCG / Salt Chlorinator)

An in-line device that generates chlorine electrolytically from dissolved pool salt, replacing or supplementing tablet / liquid chlorine dosing.

Variable-Speed Pool Pump (VFD Pump)

A pool pump with an electronically controlled motor that runs at varying RPMs to match demand. Typically cuts energy use 50–75% vs single-speed pumps.

IDPH (Illinois Department of Public Health)

The state agency that regulates semi-public aquatic facilities in Illinois under 77 Ill. Adm. Code 820. Either IDPH or delegated county health departments (Cook, Lake, DuPage, etc.) inspect and permit pools.

Bather Load

The maximum number of swimmers permitted in a pool at one time, calculated from surface area and depth. Illinois IDPH requires the number to be posted at every semi-public facility.

Fecal Incident Response

The CDC-recommended protocol for closing, treating, and reopening a pool after a fecal contamination event. Required documented procedure at every Illinois semi-public aquatic facility.

VGB Drain Cover

A federally certified suction-outlet cover that prevents entrapment hazards in public and semi-public pools. Named after the Virginia Graeme Baker Pool and Spa Safety Act (2007).

Calcium Hardness

The dissolved calcium content of pool water. Illinois IDPH accepts 150–1,000 ppm; operators target 200–400 ppm for plaster pools.

Chlorine Lock

A state in which chlorine test readings appear normal but the chlorine is ineffective at actually sanitizing the pool. Usually caused by excessive cyanuric acid.

Combined Chlorine (Chloramines)

Chlorine that has already reacted with organic contaminants and lost most of its sanitizing value. The primary cause of the strong `chlorine smell` in pools.

Cyanuric Acid (CYA / Stabilizer)

A pool additive that protects chlorine from UV degradation in outdoor pools. Essential in moderation, counterproductive above 70ppm.

Free Chlorine

The unreacted chlorine available in pool water to kill bacteria and oxidize organic contaminants. Illinois IDPH requires 1.0–5.0 ppm at all times in semi-public pools.

Langelier Saturation Index (LSI)

A composite calculation (pH + temperature + calcium hardness + alkalinity + CYA adjustment) that measures whether pool water is corrosive, balanced, or scale-forming.

pH (Pool Water)

A measure of how acidic or basic pool water is on a 0–14 scale. Illinois IDPH requires semi-public pools to hold pH between 7.2 and 7.8, with 7.4–7.6 as the practical operating target.

Pool Shock (Superchlorination / Breakpoint)

A targeted high-dose chlorine treatment that breaks apart chloramines and restores free chlorine effectiveness. Typically dosed at 10× the combined chlorine reading.

Total Alkalinity

The water's capacity to resist pH changes, functioning as a buffer. Illinois IDPH range is 60–180 ppm; operators target 80–120 ppm as a practical working band.