Lift the two carpet pieces away from each other to expose the old seam tape, then pull the tape out of the seam.
Measure the length of the seam with a measuring tape and cut a strip of new seam tape to the same measurement with scissors.
Position the new tape strip underneath the carpet seam with the adhesive facing up.
Plug a carpet seam iron into an electrical outlet and allow the iron to warm.
Lift the carpet pieces off of the seam tape and place the iron directly onto the top of one end of the tape. Wait for about 30 seconds for the iron to heat the glue on the tape.
Slide the iron about 12 inches along the seam to heat the next portion of tape. Press the carpet into the hot tape behind the iron while waiting for the iron to heat the next portion of tape.
Repeat Steps 5 and 6 for the entire length of the carpet seam.
Place a weighted board across the length of the seam to press the seam into the tape. Allow at least 30 minutes to pass before removing the board.