What are the two main causes of hardness in water?

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Prepare for the Minnesota Class D Water Operator Certification Exam with customized quizzes featuring flashcards and multiple-choice questions. Test your knowledge with detailed explanations and hints. Get exam-ready!

The primary causes of hardness in water are calcium and magnesium. These minerals are naturally occurring and are commonly found in many water sources, such as rivers, lakes, and groundwater. When water percolates through soil and rock, it can dissolve compounds that contain these metals, leading to increased hardness.

Hardness is typically measured in terms of calcium carbonate equivalent, and it can significantly impact water quality, affecting everything from household maintenance to the efficiency of water heating systems. High levels of hardness can lead to scale buildup in pipes and appliances, which can reduce efficiency and increase maintenance costs.

In summary, calcium and magnesium are the main contributors to water hardness, making option C the correct choice for this question.