What does total alkalinity measure?
- The amount of dissolved calcium and magnesium
- The total of all dissolved solids in the water
- The water's ability to resist changes in pH
- The water's ability to conduct electric current
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C. The water's ability to resist changes in pH
Alkalinity is the buffering capacity that holds pH steady when acids or bases are added. Dissolved calcium and magnesium are hardness, a different measurement.
Reference: PHTA Pool & Spa Operator Handbook, water balance chapter
Free chlorine holds steady at 2.0 ppm while the pH drifts from 7.2 up to 8.0. What happens to disinfection?
- It weakens, because less of the chlorine is HOCl
- It improves, because more of the chlorine is HOCl
- It is unchanged, because free chlorine is the same
- It stops, because chlorine cannot exist above 7.8
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A. It weakens, because less of the chlorine is HOCl
As pH rises, hypochlorous acid converts to the much weaker hypochlorite ion, so the same free chlorine reading kills more slowly. The reading alone does not tell you how much is in the active form.
Reference: PHTA Pool & Spa Operator Handbook, disinfection chapter
Where is a vacuum gauge installed on a circulation system?
- On the suction side, just ahead of the pump
- On the discharge side, just after the pump
- On top of the filter tank at the air relief
- On the return line just before the inlets
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A. On the suction side, just ahead of the pump
A vacuum gauge reads the suction the pump is pulling, so it sits on the suction side near the pump. The discharge side and the filter get pressure gauges.
Reference: PHTA Pool & Spa Operator Handbook, pumps and hydraulics
Which germ is the leading cause of diarrheal illness outbreaks linked to treated pools?
- Legionella
- Cryptosporidium
- Pseudomonas
- Staphylococcus
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B. Cryptosporidium
Cryptosporidium ('Crypto') causes most pool-related diarrheal outbreaks because normal chlorine levels do not kill it quickly. Legionella and Pseudomonas cause respiratory and skin illness instead.
Reference: PHTA Pool & Spa Operator Handbook, recreational water illness chapter; CDC Healthy Swimming
A rectangular pool is 75 ft by 42 ft with a constant depth of 5 ft. Use 7.5 gallons per cubic foot. What is the volume?
Answer in gal.
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118125 gal
Volume = L x W x D x 7.5 = 75 x 42 x 5 x 7.5 = 118,125 gal.
Reference: PHTA Pool & Spa Operator Handbook, pool math: volume