How to Vent a Bathroom Tub Drain

In certain areas of the United States, venting is required on all drainage systems.
Venting is a legal requirement in some areas.Venting is a legal requirement in some areas.
Venting allows a small amount of water to back up into the vent. This prevents back flow and bad smells from the bath drain. Installing a vent is best done before the walls of the bathroom are finished. If your bathroom is already finished you may wish to consider help from a professional contractor to reduce possible damage to the wall.

Step 1

Turn off the water to the system.

Step 2

Hold a 1 1/2-inch venting elbow up to the bathtub drain pipe. Mark on the drain pipe with a marker.

Step 3

Cut the bathtub drain pipe to accommodate the vent elbow with a hacksaw.

Step 4

Apply plumber's glue to the bathtub drain pipes and insert them into the elbow.

Step 5

Measure from the elbow to the ceiling of the room. Drill a 2-inch hole into the ceiling so the pipe can fit through.

Step 6

Apply plumber's glue to the end of the vent pipe. Insert the vent pipe into the elbow.

Step 7

Continue installing vent pipes up to the roof. Cut a hole into the roof that is 2 inches. Extend the vent pipe through the roof so it extends 6 inches above the roof grade.

Step 8

Fit a vent cap over the vent pipe. Apply roofing cement to the bottom of the cap and apply it to the roof surface to seal it.

Things You Will Need

  • Hacksaw
  • Vent elbow
  • Drill
  • Hole drill bit
  • Vent pipe
  • Vent hood
  • Roofing cement