CPI Water Quality & Treatment Standards 3

Question 1

What is the Langelier Saturation Index (LSI) used to predict in pool water?

Accepted Answer

Whether water will be scale-forming or corrosive

Answer

The LSI predicts whether water is balanced — a positive value indicates scale-forming tendency; a negative value indicates corrosive tendency.

Question 2

At what pH level does hypochlorous acid (the active sanitizing form of chlorine) exist in its highest concentration?

Accepted Answer

7.2–7.4

Answer

At pH 7.2–7.4, approximately 75–80% of chlorine exists as hypochlorous acid, the most effective sanitizing form.

Question 3

A spa inspector measures the water temperature at 104°F. What is the primary water quality concern at this temperature?

Accepted Answer

Chlorine dissipates much faster requiring more frequent dosing

Answer

Elevated spa temperatures dramatically accelerate chlorine dissipation, requiring more frequent monitoring and dosing to maintain safe sanitizer levels.

Question 4

What does a 'total dissolved solids' (TDS) reading above 1,500 ppm above the source water baseline typically indicate?

Accepted Answer

Water needs to be partially drained and replaced

Answer

High TDS (>1,500 ppm above fill water) means dissolved minerals and chemicals have accumulated to a level requiring partial drain and refill.

Question 5

Which type of algae is hardest to treat and typically requires brushing plus a specialized algaecide or high-dose chlorine shock?

Accepted Answer

Black algae

Answer

Black algae embeds its roots into plaster and grout, making it very difficult to eradicate and requiring aggressive brushing and high chlorine levels.

(CPI) Certified Pool & Spa Inspector Practice Test

(CPI) Certified Pool & Spa Inspector Practice Test

CPI Water Quality & Treatment Standards 3