How to add ventilation to a new plumbing system

October 26, 2017Blog Standard

Ventilation in a plumbing system is important for two reasons: it keeps the water present in the plumbing traps from being absorbed out by admitting air into the plumbing system, and gives sewer gases a place to ventilate. Adding an exhaust duct to a new plumbing system can be a challenge, but it is needed in most places in the United States.


  1. Locate the end of the floor cell pipe. It is the sewer pipe that ties the plumbing into the main drain. These are usually located in a central location in the house. Most modern stack pipes will be PVC construction approximately 4 inches wide.
  2. Cut a hole in any ceiling as needed for the new ventilation stack to pass through. Use the existing floor pile as a guide and measure with a plumb or level where it intersects with the new addition of ventilation with the roof. Use a jigsaw or jigsaw to cut a hole in the plaster ceiling in a circle the width of the ventilation pipe stack. Polish the rough edges.
  3. Cut a hole in the ceiling, if necessary. Continue measuring the ventilation stack up through the ceiling to where it meets the ceiling. Circle the bottom of the cover with a piece of the output stack as your guide. Nail a nail or screw through the center of the mark. Go up to the ceiling and look for the screw or nail sticking up to mark the place of the pile. Remove any shingles, shingles or other coatings within a 6-inch radius of your screw marker. Use a jigsaw to cut a hole in the bottom of the cover, using the circle as a guide.
  4. Measure and cut parts of the ventilation stack using a VI chart. This will give you the straight cut through the thick ventilation pipe. They fit the parts of the ventilation stack while working to make sure they fit tightly. Place the battery on top of the pile of soil, dry by placing them together to make sure your measurements are correct and the ventilation pipe is straight. Remove the battery parts after checking the adjustment.
  5. Starting at the top of the floor pile, apply primer, then glue, before placing the pieces together. Work your way up through the roof, attic and deck, as needed, priming and gluing the pieces.
  6. Apply construction cement to the bottom of a ceiling ventilation stack collar. Slide the collar over the stack until it is flush with the surrounding surface. Secure with nails around the perimeter of the neck. Seal the edges of the collar with tar for roofing. Replace any shingles or tiles removed around the ventilation opening.

Tips & Warnings

  • Always check local plumbing codes in your area before adding a ventilation flue for a new plumbing system.
  • Be careful when working on ceilings.

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