How to Add Plumbing to a PVC Vent Stack

New drain plumbing requires a vent pipe connection to the vent stack.

The plumbing vent stack lets air enter the home’s waste-drain-vent system and lets sewer gas escape. Both are essential functions for keeping your home's drainpipes safely working. New fixtures requiring new drain or waste pipes also require a new vent. The new plumbing’s connection o the vent stack is governed by building codes. A permit is needed before starting work.

Things You'll Need

• T-fitting
• Permanent marker
• Saw
• Rag
• PVC pipe and fittings
• PVC primer
• PVC cement

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Instructions

1. Hold the T-fitting against the PVC vent stack at the connection point. The wider portions of the T are called hubs. The pipes fit into the hubs. Marking the hub depths on the vent stack with the permanent marker shows where to cut the stack. The removed stack portion is shorter than the T-fitting’s length.

2. Hold the vent stack pipe’s upper portion in place. Cut the vent stack pipe with the saw at both marks. Lift the stack’s upper portion enough to temporarily slip the T fitting into place.

3. Dry fit additional PVC pipe and fittings without cement between the new drain or waste pipe and the new T on the vent stack. Marking each fitting and pipe shows how they align with each other, including the vent stack and the new fitting on the stack. Do not glue any pipes yet. Temporarily plug the remaining hub on the T with a rag.

4. Lift the vent’s upper portion off the Tee fitting and hold it up. Open the PVC primer can and wipe the dauber around the outside of each cut end of the vent stack. Dip the dauber in primer after each application. Add more primer to the T-fitting hubs’ inside. Replace the primer cap.

5. Open the PVC cement and remove the dauber. Wipe glue around the outside of each cut end of the vent stack, and around the inside of the two hubs that fit onto the vent stack. Place the T fitting onto the stack. Lower the upper portion into the fitting and turn the fitting one-quarter turn aligning the marks made on the stack with the marks made on the fitting.

6. Prime and cement the pipes and fittings connecting the new plumbing to the vent stack’s new T fitting. Each connection consists of a hub and pipe end. Prime and cement each hub and pipe end.

Tips & Warnings

• The marks show how the fittings align with the pipes. As you cement each fitting and pipe together, turning the fitting one-quarter turn spreads the cement evenly. Holding the fittings and pipes together for 30 to 60 seconds prevents separation.

• The vent stack can be heavy, especially below the attic level. Have a helper hold the stack or use a strap wrench to support it.

• The gases that escape through the vent stack are harmful if concentrated. Have everything ready before you cut the pipe, and then install the T as quickly as possible.

References

• Plumbing 1-2-3; The Home Depot