What water quality problem is most likely to occur at dead-end water mains?

Dead-end water mains can contribute to specific water quality issues primarily due to stagnation, which is the result of limited water flow. When water remains stagnant in any section of a distribution system, it can lead to a concentration of various compounds and changes in the water's characteristics.

Taste and odor issues in water can arise from a couple of factors inherent to dead-end water mains. Bacterial growth can happen in stagnant water, leading to the production of metabolites that impact the taste and odor. Additionally, longer residence time can allow for the leaching of materials from the pipes or fixtures, especially if they contain organic compounds that may impart unpleasant tastes or odors.

Thus, given the context of stagnant water in dead-end lines, the likelihood of experiencing taste and odor problems makes this the correct answer. The other choices pertain to different water quality issues that are either less likely or not specifically correlated with the situation presented in dead-end mains.