: I am remodeling my batroom sink. I noticed that the old sink drain vent does not go up through the attic and roof. It stops about 2 feet vertically after the p-trap makes a 90 degree bend and then another 90 degree bend pointing down. There is some sort of cap on the end that is covered with a wax substance. This is all behind the drywall. Is this some kind of vent system? Should I make a proper vent for this sink? The main vent for the toilet and shower is about 10 feet away. The house is about 30 years old. Thanksproper vent! there is no vent, the vent should be installed at the point were the 2 ft. trap arm drops down. take out 90 install T-Y. continue vent to attic and tie into existing.
