Vent openings on reservoirs and clear wells should be?

The correct choice for vent openings on reservoirs and clear wells being screened is based on the need to maintain water quality and system integrity while still allowing for necessary ventilation.

Screening vent openings serves to prevent contaminants, debris, or pests from entering the water supply while allowing air exchange. This is particularly important in maintaining the pressure balance within the reservoir or clear well, which can help prevent vacuum conditions that could potentially draw in unwanted materials. Additionally, proper screening helps to protect the water from external environmental factors that could compromise its cleanliness or safety.

Each of the other options fails to offer the same level of protection. If vents are simply open, they would provide no barrier against contaminants. Covering the vents, on the other hand, might restrict ventilation and cause pressure issues. Locking them can prevent access but doesn’t provide the necessary air exchange or protect against ingress of contaminants. Hence, the best practice is to use screens.