What is the required visibility distance for the black disk in a swimming facility?

In swimming facilities, the black disk is utilized as a visual cue to help determine the clarity of the water. The required visibility distance for the black disk is generally set at 9 meters, which means that when submerged in the water, the disk must be clearly visible from this distance.

This standard ensures that the water quality is safe for swimmers, as poor visibility can indicate higher levels of turbidity, which may lead to health risks. Maintaining a visibility distance of 9 meters helps operators assess the effectiveness of filtration and sanitation processes. If the disk is visible at this distance, it reflects that the water is adequately clear and safe for swimming activities.

Standards may vary slightly depending on local regulations and guidelines, but the 9-meter visibility is a widely accepted benchmark across many aquatic facilities.