What are the design requirements for venting wet wells, dry wells, basins, tanks and reservoirs?
• All wet wells, dry wells, basins, tanks and reservoirs require venting. Wet and dry wells require forced ventilation and basins, tanks and reservoirs require normal ventilation. Wet wells require 12 continuous air changes per hour or 60 intermittent air changes per hour based on the volume of the head space above the minimum sewage level. Dry wells require six continuous air changes per hour or 30 intermittent air changes per hour based on the volume of the dry well. Wet wells and dry wells are usually vented by force draft fans or blowers in combination with odor control devices located on the ventilation discharge from the wet or dry well. National Fire Protection Association (NFPA) Section 820 specifies that all continuous ventilation systems should be fitted with flow detection devices connected to an alarm system to indicate ventilation system failure. Basins, tanks and reservoirs are usually vented using inverted ‘U’ type, ‘chair’ or cross-flow vents using normal air currents.
