How to Vent a Sink Drain

Michael Straessle

When water drains slowly from a sink even if you know the pipes are clear, the problem may be the result of a poor or absent vent. For a drain to work properly, it must be vented so air can escape the pipe.

Installing a vent on an existing drain is a project that any homeowner can accomplish if they do their homework and learn as much as possible before starting. When using an inline vent, be sure to match it with the type of drain pipes used.

  1. Relocate all items stored under the sink to a safe place, out of the reach of children. Locate the drain line coming from the wall. This pipe will connect to the P-trap.

  2. Remove this section of the drain line from the wall connection and the P-trap. Measure the distance between the wall and the P-trap to determine how much of the pipe can be removed to add the T connection. Make a note of this measurement.

  3. Cut the pipe with a handsaw. Clean the burrs off the cut edges with a sanding block.

  4. Apply PVC primer to the ends of the pipe, followed by PVC glue. Insert the pieces into the T section of the T connection, twisting them slightly when they seat to ensure a good bond.

  5. Apply PVC primer followed by PVC glue to the end of the inline vent and insert it into the remaining end of the T connection. Next, measure the finished product and compare it with the measurement from Step 2. Adjust the length as necessary.

  6. Insert the pipe with the inline vent into the wall connection and align it with the P-trap. Secure both ends of the drain line until the nuts are tight.

  7. Tip

    Be sure to twist the pipes slightly when making a new connection to help the adhesive bond well. Place newspaper or an old cloth on the floor or table to protect it from the PVC primer and glue that may drip from the applicators during assembly of the pipes.


    Do not use PVC primer and glue without proper ventilation.

    Do not leave PVC primer, glue or tools unattended in the presence of children.