Studor 20302 Maxi-Vent 3-Inch to 4-Inch Air Admittance Valve …
Save $ -57.55
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. 1ATD5 vents up to 500 DFUs on a stack; 1ATD6 vents up to 160 DFUs on a branch and up to 24 DFUs on a stack. 15W940 has a replaceable cabon filter to reduce plumbing drainage system odors.