CWS CWS Hardness, Scale & Corrosion Control 2 — Questions and Answers
Question 1: Which treatment method is most commonly used to prevent scale formation in residential water systems?
- Activated carbon filtration
- Ion exchange water softening (Correct answer)
- Ultraviolet disinfection
- Sediment filtration
Correct answer: Ion exchange water softening
Ion exchange water softeners replace calcium and magnesium ions with sodium ions, preventing the precipitation of hardness minerals that form scale.
Question 2: Template Assisted Crystallization (TAC) media prevents scale by:
- Removing calcium and magnesium from water
- Converting dissolved hardness minerals into non-adherent microscopic crystals (Correct answer)
- Adding polyphosphates to the water
- Raising water pH above 9
Correct answer: Converting dissolved hardness minerals into non-adherent microscopic crystals
TAC media nucleates hardness minerals into stable microscopic crystals that remain suspended in water rather than adhering to pipe walls, without adding sodium or removing minerals.
Question 3: Polyphosphate injection is used in water treatment primarily to:
- Kill bacteria
- Sequester iron and prevent scale on pipes (Correct answer)
- Soften hard water
- Reduce turbidity
Correct answer: Sequester iron and prevent scale on pipes
Polyphosphates sequester (bind to) iron, manganese, and calcium ions in solution, preventing them from forming deposits on pipe walls and equipment.
Question 4: What grains per gallon (gpg) level is generally considered the threshold for 'very hard' water in the US?
- Over 3.5 gpg
- Over 7 gpg
- Over 10.5 gpg (Correct answer)
- Over 14 gpg
Correct answer: Over 10.5 gpg
Water hardness above 10.5 gpg is classified as very hard by most US water quality guidelines, while 3.5–7 gpg is moderate and 7–10.5 gpg is hard.
Question 5: A customer's water heater is losing efficiency and has reduced hot water output. The most likely cause related to water quality is:
- High chlorine residual
- Scale buildup from hard water on the heating element or tank walls (Correct answer)
- Iron staining inside the tank
- Low water pressure
Correct answer: Scale buildup from hard water on the heating element or tank walls
Scale deposits from hard water act as insulation on heating elements and tank walls, reducing heat transfer efficiency and increasing energy costs.
Question 6: Which pH range is generally considered mildly corrosive to copper plumbing?
- pH 8.0–8.5
- pH 7.0–7.5
- pH 6.5–7.0
- Below pH 6.5 (Correct answer)
Correct answer: Below pH 6.5
Water with pH below 6.5 is acidic enough to aggressively attack copper pipes, leaching copper into the water and causing pinhole leaks over time.
CWS CWS Hardness, Scale & Corrosion Control 2
Which treatment method is most commonly used to prevent scale formation in residential water systems?