AFO Aquatic Facility Operator key terms

The portion of chlorine in pool water that remains available to kill pathogens and oxidize contaminants; it is measured as free available chlorine and is the primary disinfection residual operators monitor.

Chlorine that has already reacted with nitrogen-containing wastes such as sweat, urine, or ammonia; it is much weaker as a disinfectant and is calculated as total chlorine minus free chlorine.

Nitrogen-chlorine compounds formed when chlorine binds with ammonia or other nitrogenous contaminants; they cause the characteristic pool smell, irritate eyes and airways, and signal a need to oxidize or shock.

A logarithmic measure of how acidic or basic the water is, on a scale from 0 to 14; pool operators typically target 7.2 to 7.8 because pH strongly affects disinfection efficiency and water balance.

The water's capacity to resist changes in pH, mainly from bicarbonate, carbonate, and hydroxide ions; proper alkalinity helps stabilize pH and is usually maintained around 80 to 120 ppm.

The concentration of dissolved calcium in pool water, usually expressed as ppm calcium carbonate; too low can corrode or etch surfaces, while too high can cause scaling and cloudy water.

A stabilizer that protects free chlorine from destruction by sunlight; it is common in outdoor pools but excessive levels can reduce chlorine's effectiveness and are managed by dilution.

The point at which enough chlorine has been added to oxidize all combined chlorine and nitrogenous waste, producing a sharp drop then rise in free chlorine; often used to resolve chloramine problems.

Oxidation-reduction potential, measured in millivolts, is an electronic reading of the water's oxidizing strength; it responds to sanitizer activity and is used by controllers to automate chlorine feed.

A calculated number that predicts whether water will tend to deposit calcium scale or dissolve calcium from surfaces; it combines pH, temperature, calcium hardness, total alkalinity, and dissolved solids.

Compounds such as chloramines, trihalomethanes, and haloacetic acids that form when disinfectants react with organic matter in water; they can irritate swimmers and are controlled by good circulation, filtration, and fresh water.

Adding a large dose of chlorine to oxidize contaminants and destroy chloramines, often called shocking; it requires keeping bathers out until free chlorine falls to a safe level.

The time required to circulate a volume of water equal to the entire pool through the filtration system; it is expressed in hours and used to evaluate whether circulation is adequate for the pool's volume and use.

The volume of water moving through a pipe or system per unit of time, commonly measured in gallons per minute; it must match the design of pumps, filters, and drains to keep circulation and treatment effective.

The loss of pressure energy as water flows through pipes, fittings, filters, and other components, usually measured in feet of head; excessive head loss reduces flow and increases pump energy use.

Reversing water flow through a filter to dislodge trapped debris and flush it to waste; it is performed when pressure differential or a set schedule indicates the filter is loading up.

The material inside a filter that captures particles, such as sand, anthracite, diatomaceous earth, or cartridge fabric; media type and condition determine filtration effectiveness and required flow rates.

A surface intake that draws water and floating debris from the pool surface into the circulation system; proper water level and weir operation are needed for skimming to work.

An outlet, usually at the pool's deepest point, that returns water to the circulation system; it must be fitted with an approved anti-entrapment cover and can be a serious entrapment hazard if missing or broken.

A holding tank that absorbs water displaced by bathers and keeps the pool water level stable so the circulation system can operate evenly; common in pools with gutter or overflow designs.

The network of drains, pipes, pumps, filters, and returns that moves pool water from the pool, treats it, and returns it; its design and balance determine circulation, filtration, and chemical distribution.

The height of the pool water relative to the skimmer or overflow system; it must be maintained within a narrow range to allow skimming, avoid pump air intake, and keep the pool operating properly.

The cloudiness of water caused by suspended particles; high turbidity can shelter pathogens, reduce visibility for safety, and indicate filtration or chemistry problems.

A manufacturer's graph showing the relationship between a pump's flow rate and the head it can develop; operators use it to understand performance and diagnose reduced flow.

Formation and collapse of vapor bubbles in a pump when inlet pressure is too low; it causes noise, vibration, and damage, often from a blocked suction line or excessive suction lift.

The number of people in or around a pool at a given time, or the maximum number allowed by design or code; it influences circulation, sanitation demand, staffing, and safety supervision.

A hazardous condition in which a swimmer is held underwater by suction or body or limb contact with an outlet, drain, or other fitting; prevention relies on compliant covers, dual drains, and emergency shutdown.

The Virginia Graeme Baker Pool and Spa Safety Act is a U.S. federal law requiring anti-entrapment drain covers and other safety measures in public pools and spas to prevent suction entrapment.

A fitted cover over a pool outlet that is designed to prevent body or limb entrapment and hair entanglement; it must be approved, securely attached, uncracked, and matched to the outlet's flow.

A written, practiced procedure describing how staff respond to injuries, entrapments, chemical releases, weather, and other emergencies; it assigns roles, communication steps, and rescue equipment.

The specific water area assigned to a lifeguard for continuous watching; it should be clearly defined, free of blind spots, and manageable given bather load, glare, and distractions.

A documented procedure for clearing and disinfecting the pool after feces enter the water; the response depends on whether the stool is formed or diarrheal and includes closure, removal, disinfection, and recordkeeping.

A standardized document provided by chemical manufacturers that lists hazards, handling precautions, first aid, and spill response for a product; it must be accessible to staff who use pool chemicals.

Protective clothing and gear such as gloves, goggles, aprons, and respirators worn when handling chemicals or performing maintenance; it reduces exposure to splashes, fumes, and injuries.

A lift or other accessible means required by the Americans with Disabilities Act to help people with disabilities enter and exit a pool; it must be maintained, operational, and available during open hours.

Maintaining logs of water tests, chemical additions, maintenance, accidents, and training; good records support trend analysis, regulatory compliance, and defense of facility operations.