How to Plumb a Sink Drain Vent

When remodeling a kitchen, bathroom or building, it is important to take into account all the plumbing needs. One thing that is easily forgotten but essential to proper operation is the venting of the sink drain. A sink drain without a proper vent can become very hard to drain. The purpose of the vent is to allow for air to escape from the drain line so that water can flow. It also gives the sewage gases somewhere to escape to instead of through the drain. The process of venting a sink drain is not too difficult to complete.

Things You'll Need

• PVC pipe equal to the size of the drain-1 1/2 inches is most common
• Drain tee
• Air admittance valve
• PVC cleaner and cement
• Fittings for corners

Instructions

Open Wall

1. Install a tee at the level of the drain in the wall. The tee side of the tee works for the drain, and the top side works as the vent.

2. Install PVC pipe in the top of the tee. The pipe needs to run through the wall all the way through the roof.

3. Install a flashing boot around the vent pipe through the roof. Use this method for full remodels and new construction. Any runs parallel with the floor should have fall from the high side to the low side.

Without Removing Wall Board

1. Cut the sink drain pipe under the sink just before it enters the wall. Cut no closer than 2 inches to the wall.

2. Install a PVC tee at the location of the cut. Use a straight line for the drain, and use the tee for the vent. Make sure the tee is vertical, straight up.

3. Install a 2-inch piece of pipe in the top of the tee.

4. Install the air admittance valve on top of the 2-inch piece of PVC pipe. This valve will allow air to exit the system and allow the drain to work properly.

Tips & Warnings

• The air admittance valve is the easiest way to fix a sink without a vent.

• Install the air admittance valve according to the manufacturer's instructions.

• PVC glue and cleaner are highly flammable.

• PVC Glue and cleaner are toxic if inhaled in large quantities.

References

• How to Plumb a Small Half Bath
• How to Plumb an Island Sink

Resources

• Read this Article in Spanish