Impacts of Water Hardness — Which statement correctly identifies what hardness does NOT do?

Introduction:
Hardness in water is due to calcium and magnesium ions. While it creates several operational and aesthetic problems, moderate hardness is generally not a direct health hazard. This question asks you to identify what hardness does not do among the listed effects.

Given Data / Assumptions:

• Hardness levels typical of raw ground- and surface-waters.
• Boiler operation is sensitive to scale formation.
• Soaps form insoluble salts with Ca2+/Mg2+, reducing lathering efficiency.

Concept / Approach:

In boilers, hardness precipitates as scale (for example, CaCO3, CaSO4), which lowers heat-transfer efficiency and can cause damage—so it certainly has adverse effects. In cooking, hardness prolongs softening of foods like legumes. In laundering, soap scum forms and detergent demand increases. However, moderate hardness by itself does not make water unfit for drinking; many guidelines set acceptable ranges for hardness for taste and scaling control, not for toxicity.

Step-by-Step Solution:

Verification / Alternative check:

Standards provide guideline values for hardness primarily for scaling/taste; there is no acute toxicity at typical environmental concentrations of Ca2+ and Mg2+ in drinking-water.

Why Other Options Are Wrong:

A: False—hardness clearly causes boiler scale. B and D are well-documented operational issues. E is a corollary of D in detergent systems.

Common Pitfalls:

Assuming “hard water is unsafe.” Safety concerns relate more to contaminants such as heavy metals, pathogens, or nitrates, not calcium/magnesium hardness.

Final Answer:

Hardness makes water unfit for drinking on health grounds alone.