AFO Aquatic Facility Operator cheat sheet

Free chlorine = HOCl (hypochlorous acid) + OCl⁻ (hypochlorite ion); HOCl does the killing, and its share falls as pH rises - roughly 75% at pH 7.0, 50% at pH 7.5, and 25% at pH 8.0.

Combined chlorine = total chlorine − free chlorine. It is mostly chloramines, causes the 'chlorine odor' and eye irritation, and should be kept below 0.2 ppm; many codes close a pool above 0.5 ppm.

Breakpoint chlorination: add about 10× the measured combined chlorine as free chlorine. The residual first falls as chloramines are destroyed, then rises sharply once breakpoint is passed.

Cyanuric acid protects free chlorine from sunlight but slows kill times. Typical target 30–50 ppm; most codes cap it at 100 ppm and some require dilution above that.

1 lb of 65% calcium hypochlorite in 10,000 gal raises free chlorine about 8 ppm; 1 lb of 56% sodium dichlor adds about 6.5 ppm free chlorine and roughly 7 ppm cyanuric acid.

Control pH in the 7.2–7.8 range. Below 7.2 the water is corrosive to metal and plaster and irritating to eyes; above 7.8 disinfection efficiency drops and scaling risk climbs.

Total alkalinity of 80–120 ppm buffers pH. Below about 60 ppm pH bounces with every chemical addition; above about 150 ppm pH is hard to lower and scaling increases.

Calcium hardness 200–400 ppm. Below about 150 ppm water is aggressive (etches plaster, corrodes metal); above about 500 ppm scale forms on heaters, tile, and filter media.

Langelier Saturation Index = pH + temperature factor + calcium factor + alkalinity factor − TDS factor. Keep it between −0.3 and +0.3, slightly positive, to avoid both corrosion and scaling.

Turnover time (hours) = pool volume (gal) ÷ flow rate (gpm) ÷ 60. Common code minimums: 6 hours for swimming pools, 1 hour for wading pools, 30 minutes for spas.

Required flow (gpm) = volume (gal) ÷ (turnover hours × 60). A 50,000-gallon pool on a 6-hour turnover needs about 139 gpm.

Filter loading rates: rapid sand 12–20 gpm/ft², high-rate sand 15–20 gpm/ft², diatomaceous earth 1–2 gpm/ft², cartridge 0.25–0.375 gpm/ft². Exceeding the rate drives media and debris into the pool.

Backwash sand filters at 15–20 gpm/ft² until the sight glass runs clear (typically 2–3 minutes), then rinse 15–30 seconds before returning the multiport valve to Filter.

Backwash when the influent gauge reads 8–10 psi above its clean starting value or when flow drops below the code-required rate - not on a fixed calendar alone.

Sand media specification: #20 silica, effective size 0.45–0.55 mm, uniformity coefficient of 1.5 or less, bed depth 24–30 inches.

Each skimmer is designed for about 30–40 gpm and needs water level at the middle of the weir throat; a weir riding high, a vortex in the basket, or a dry skimmer signals a flow imbalance.

Filtration removes suspended particles only. Dissolved waste and microorganisms are removed by oxidation and disinfection, so clear filtered water is not automatically safe water.

All suction outlets need VGB-compliant covers matched to their frames; single-blockable outlets require dual drains, an SVRS, or another approved backup, with grate velocity limits set by the health code.

Bather load = water surface area ÷ 20 ft² per bather in water deeper than 5 ft, and ÷ 15 ft² in water 5 ft or shallower; the lowest result from pool, deck, and amenity limits governs.

Depth markers are required at the waterline and on the deck at the minimum and maximum depths, at both ends and at regular intervals along the sides; a float line marks the 5-ft break to deep water.

Chemical storage rule: oxidizers and acids go in separate cabinets or separate rooms, never stacked one above the other, with secondary containment sized for the largest container and no shared scoop or funnel.

Suspected spinal injury: stabilize the head in line with the spine, support the victim in the water, and remove them only if the airway is compromised or the scene is unsafe.

Rescue equipment per pool: a rescue tube for each guard on duty, a reaching pole of 10–12 ft, a ring buoy with 40–50 ft of line, a first aid kit, an AED, and an accessible phone.

Drowning is the leading cause of unintentional injury death for children ages 1–4; four-sided isolation fencing with a self-closing, self-latching gate is the most effective single barrier.

The emergency action plan must be written, posted, and rehearsed, with named roles for rescue, calling 911, crowd control, and EMS access; drills are logged with date, scenario, and participants.

Risk management sequence: identify the hazard, evaluate exposure, apply controls in order (eliminate, guard, warn, train), then monitor and document the result.

Incident reports are written with facts only - time, place, people, witnesses, actions taken, and notifications - with no opinions, blame, or speculation about cause.

Cavitation - rumbling pump, low flow, air in the strainer - comes from the suction side: clogged basket, closed valve, undersized or blocked suction line, or low pool water level. It damages the impeller.

Multiport valve positions are Filter, Backwash, Rinse, Waste, Recirculate, and Closed. Never move the handle while the pump is running; the pressure surge can rupture the valve or plumbing.

Clean the pump strainer basket daily. A full basket throttles suction flow, raises vacuum at the gauge, and can collapse the basket or crack the pump pot.

Water dripping from beneath the pump housing indicates a failed shaft seal, which also admits air into the suction and causes loss of prime and cavitation.

Test ground-fault circuit interrupters serving pool equipment monthly using the test button and record the result; NEC Article 680 governs bonding and grounding of pool equipment.

Scale on a heater heat exchanger comes from high pH, high calcium hardness, or high total alkalinity; the deposit insulates the tubes, cuts heat transfer, and can restrict flow enough to trip safety switches.

A flow or pressure switch prevents a heater from firing without water flow; a failed switch is a common cause of 'no heat' calls even when the heater itself is sound.

Preventive maintenance cadence: daily basket, readings, and clarity; weekly backwash, skimmer check, and feeder check; monthly GFCI test and gauge comparison; annually media inspection, heater service, and pump rebuild review.

Calibrate test kits and electronic controllers against a known standard and replace reagents before expiration, because stale DPD reagent reads falsely low and can hide a chlorine deficiency.

Log free chlorine, combined chlorine, pH, flow rate, temperature, and clarity at opening and again during the day; most codes require a written record kept on site and retained for a set period.

Water clarity standard: the main drain must be clearly visible from the deck at the deep end. If it cannot be seen, close the pool until filtration and chemistry restore clarity.

Zone coverage follows the 10/20 rule - 10 seconds to recognize a victim and 20 seconds to reach them - with one guard assigned per zone and no overlapping or unassigned water.

Rotate lifeguards every 20–30 minutes to counter vigilance decrement, and document the rotation; a guard moved to a new zone must be briefed on that zone's hazards.

Pre-service training is completed and documented before an employee's first shift; in-service training of at least 4 hours per month keeps rescue, CPR, and AED skills current.

Opening checklist: uncover and inspect, confirm water level and clarity, test chemistry, verify flow and filter status, stage rescue equipment, unlock gates, and record readings.

Closing checklist: clear and count bathers, secure and lock chemicals, cover where applicable, record final readings, lock gates, and set alarms.

AFO and CPO operator credentials are typically valid for 5 years and are renewed through continuing education and a recertification exam; keep the certificate posted or on file for inspection.

Enforce bather load and facility rules with posted signage at entrances and at the deck; capacity limits apply separately to the pool, spa, and wading pool.

The CDC Model Aquatic Health Code (MAHC) is a model, not law. It becomes enforceable only where a state or local health department adopts it, sometimes with amendments.

The Virginia Graeme Baker Pool and Spa Safety Act requires VGB-compliant anti-entrapment drain covers on all public pools and spas, plus a backup system for single-blockable outlets: dual drains, SVRS, or another approved device.

OSHA Hazard Communication (29 CFR 1910.1200) requires a safety data sheet on hand for every chemical, labeled containers, and documented employee training on those hazards.

OSHA Bloodborne Pathogens (29 CFR 1910.1030) requires a written exposure control plan, PPE, and hepatitis B vaccination offered to at-risk staff.

ADA requires an accessible means of pool entry - lift, sloped entry, or transfer wall - plus accessible routes to the deck and compliant signage.

CDC fecal incident response, formed stool: remove it, raise free chlorine to 2 ppm at pH 7.5, and hold 25 minutes (CT 9.0) before reopening.

CDC fecal incident response, diarrheal stool: remove it, raise free chlorine to 20 ppm at pH 7.5, and hold 12.75 hours (CT 15,300); hyperchlorinate and confirm the residual before reopening.

Many jurisdictions require notification of the health department for fecal or vomit incidents, chemical overexposures, and injuries requiring EMS transport.

Inspection readiness: posted permit, current operator certification, working emergency phone, correct depth markers and signage, VGB covers, and a completed self-inspection form on file.