Sometimes space restrictions require the installation of Big Dipper units in basement locations where significant head pressure becomes a factor. The Big Dipper VFCA-20 Vented Flow Control module provides an option for use with installations where significant head pressure is present (greater than 6' [1.95 m]) or where applicable regulations require vented flow controls. The Vented Flow Control helps reduce problems associated with high head pressure and helps slow the drainwater flow down the pipe, preventing it from exceeding 20 gallons per minute (1.26 l/s). Includes appropriate PVC fitting and flow stainless steel flow control orifice.