CRYSTAL AQUATICS POOL OPERATOR
EXAM QUESTIONS WITH COMPLETE
SOLUTIONS
Sodium hypochlorite - Answer-Liquid chlorine, strong oxidizer with high pH
Range 1.5 - 4 ppm or ORP 650 - 750 mV
Chlorine gas - Answer-Most effective, 100% FAC, dangerous
Electrolysis (salt based Chlorine generation) - Answer-NaCl added to pool water, runs
through salt cell. Electric charge applied to plates, breaks Na off to form hypochlorous
acid
Combined chlorine - Answer-Abbreviated CC's, a.k.a. chloramines. Free chlorine acts
with contaminants to form these.
Total chlorine - free chlorine = combined chlorine
TC - FC = CC
If CC is above 0.2 ppm, super chlorinate pool
Super chlorination - Answer-Point at which all contaminants are oxidized
FC level must be raised to at least 10x CC level. If CC is 0.3 ppm, then 10x0.3 = 3
hyperchlorination - Answer-Hyperchlorination disinfects water and kills bacteria and
parasites. Raise Cl for a period of time, based on pathogen inactivation value.
Breakpoint Cl level - FC level = ppm change needed to hyperchlorinate
Cyanuric acid (CYA) - Answer-Water conditioner that stabilizes chlorine after exposure
to UV radiation
Maintain at 30 - 50 ppm
Not effective with bromine
More CYA = longer it takes to kill bacteria
pH - Answer-quantification of hydrogen ion concentration in a solution
ideal 7.5, range 7.2-7.8
Liquid Cl causes a rise in pH
Gas Cl causes a drop in pH
If high, add muriatic acid
If high, water scales: clouds water, blocks filters, white film
If low, add sodium carbonate (soda ash)
, If low, water is corrosive: stains surfaces, corrodes whitecoat, dissolves metal
Alkalinity - Answer-Ideal 80-120 ppm
Total alkalinity is water's ability to resist pH changes
If high, add muriatic acid
If high, water scales: clouds water, blocks filters, white film
If high, pH drifts upward
If low, add sodium bicarbonate
If low, water is corrosive: stains surfaces, pits concrete, dissolves metal
If low, pH bounces and is difficult to maintain
Calcium hardness - Answer-Ideal level 200-400 ppm
Calcium hardness: measure of calcium concentration in water
High Ca and Mg concentration = hard
Low Ca and Mg concentration = soft
If high, dilute with soft water
If high, water is scaling: clouds water, plugs filters, creates white film
If low, add calcium chloride
If low, water is corrosive: pits concrete and etches plaster
Temperature - Answer-Ideal pool 78-82 Fahrenheit, spa 104 Fahrenheit
High temperatures in spas = more likely to scale
Low temperatures in winterized pools = more likely to corrode
High temperatures in pools makes Chlorine break down faster
Disinfectants work effectively in ideal temp range
Saturation index - Answer-SI is the calculation used to determine if water is balanced
If low (below -0.3) it's corrosive with concrete etching and metal corrosion
If high (above 0.3) there is cloudiness and scaling
Contact time - Answer-CT values: amount of time necessary for inactivating pathogens
in the water
CT inactivation level / Chlorine level = time required to inactivate
Total dissolved solids - Answer-TDS is the measure of all organic and inorganic
dissolved solids in pool water
Increase due to solids like minerals, salts, metals in pool
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