What conditions could lead to sediment accumulation affecting sight glass readings?

Sediment accumulation in sight glasses can often be attributed to poor water quality. When the water quality is compromised, it may contain higher levels of impurities or minerals, which can settle and form sediment. This build-up can obstruct sight glasses, leading to inaccurate readings or difficulties in monitoring the water level.

Factors like low boiler temperature might not necessarily lead to sediment accumulation; instead, they could affect the overall efficiency of the system. High operating pressure typically deals with the system's performance under stress rather than sediment build-up. Frequent water changes may actually reduce sedimentation, as they help maintain better water quality by regularly refreshing the water and removing contaminants.

Thus, poor water quality directly correlates with the presence of sediments that impair the sight glass readings, making it the correct answer in this context.