Larger ponds will have seams in the liner—and you’ll need to learn how to join them properly to prevent leaks. The process can differ slightly depending on whether the flexible liner is PVC or EPDM. PVC liners will require you to overlap each piece of liner by several inches, then use a contact cement approved for use with pond liners to coat the front and back of the material along the seam. Press the seams together and allow the cement to cure.
EPDM pond liners typically require seam tape. You’ll need to prime the seams with an adhesive priming spray, then apply the seam tape to the bottom layer of the liner. Once in place, remove backing tape from the seam tape and press the top layer down, making sure to use a roller to ensure a tight seal.
