Studor 20297 Maxi-Filtra Septic Tank Drain Vent Two-Way Active Carbon Filter

Allow air to enter DWV systems to equalize pressure when water drains out of the system; eliminate the need for costly roof penetrations and vent piping. No. 1ATD5 vents up to 500 DFUs on a stack; No. 1ATD6 vents up to 160 DFUs on a branch and up to 24 DFUs on a stack. No. 15W940 has a replaceable cabon filter to reduce plumbing drainage system odors.