CPO Pool Maintenance and Troubleshooting 2

Question 1

Pool water appears cloudy despite free chlorine and pH being within normal range. What is the most likely cause?

Accepted Answer

Poor filtration or inadequate water circulation

Answer

Insufficient total alkalinity below 80 ppm

Answer

Excessive calcium hardness above 400 ppm

Answer

Cyanuric acid levels above 50 ppm

Question 2

A pool has developed a widespread green algae bloom. What is the recommended initial treatment?

Accepted Answer

Shock the pool with chlorine at approximately 10 times the normal dose

Answer

Add copper-based algaecide and resume normal filtration

Answer

Raise pH to 8.0 to create a hostile environment for algae

Answer

Drain the pool by 50% and refill with fresh water

Question 3

Mustard (yellow) algae is particularly difficult to eliminate because it:

Accepted Answer

Is resistant to normal chlorine levels and clings tightly to pool walls

Answer

Only grows in pools with pH above 8.0

Answer

Cannot be treated with any chlorine-based product

Answer

Reproduces only in heated pools above 85°F

Question 4

Black algae is the most difficult pool algae to eliminate primarily because:

Accepted Answer

It has a protective outer layer and deep roots that penetrate porous surfaces

Answer

Standard chlorine products have absolutely no chemical effect on it

Answer

It only grows in areas with zero UV light exposure

Answer

Pool filters are unable to remove its reproductive spores

Question 5

A sand filter's clean operating pressure is 10 psi. At what pressure reading should backwashing be initiated?

Accepted Answer

15–18 psi (5–8 psi above clean starting pressure)

Answer

When pressure drops below 5 psi

Answer

Every 24 hours regardless of the gauge reading

Answer

When pressure doubles to exactly 20 psi

Question 6

After backwashing a sand filter, what step should be performed before returning to normal filtration mode?

Accepted Answer

Run on the 'rinse' setting for 30–60 seconds to re-seat the sand bed

Answer

Immediately switch the multiport valve back to filter mode

Answer

Add fresh filter sand to replace any lost during backwashing

Answer

Shock the pool to compensate for any chlorine dilution

Question 7

At a pool pH of 7.5, approximately what percentage of free chlorine exists as the active hypochlorous acid (HOCl) form?

Accepted Answer

About 50%

Answer

About 25%

Answer

About 75%

Answer

About 10%