How to Install a Horizontal Plumbing Stack Vent

A horizontal plumbing stack vent installs on the horizontally opposed drain line leading into your main stack. This vent usually connects to the toilet drain line but may also service a faucet drain. You must look beneath the floor under your toilet or faucet to locate the toilet drain line. After you locate the drain pipe, simply follow it until you come to a 4-inch diameter pipe, which is the home's main drainage stack. Install the vent where you find a suitable place with enough clearance for the vent pipe.

Things You'll Need

Hacksaw
PVC fitting
Reducing fitting, if applicable

Air vent
PVC adhesive

Instructions

- 1
  Cut the drain line with a hacksaw after you establish where the vent is to go. It needs to be in a place free of obstructions. Normally, vents are fitted at the joint where the drain connects to the stack.
- 2
  Install a PVC T-fitting in between the two pipes where you made the cut. Slide one end of the drain pipe into the fitting and then install the other end in the other side of the fitting. If you connect the fitting directly to the 4-inch drain pipe, ensure you use a reducing fitting that has both a 3-inch and 4-inch side. If you are cutting near the T-fitting that connects the drain line to the main stack, don't make the cut right next to the fitting. Cut the pipe 3 inches from the joint so there is ample pipe left over to slide the fitting on.
- 3
  Push the vent inside the top inlet of the fitting. Adjust the fitting if the vent does not fit properly. Take the air vent out of the fitting and remove the fitting.
- 4
  Spread PVC adhesive around the edge of the fitting inlets and air vent. Cover the edges of the drain and main drain stack pipes with PVC adhesive. Re-install the vent and fitting. Let them both sit to dry for at least four hours.

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