Pond Liner should be spliced together on a flat, even, clean surface. Driveways are good so are decks or patios. Lawns are bad, since they are uneven and cushioned by the grass. If the length that you are splicing together is very long, make sure that is is all laid out flat and even before you start. If you try to unroll as you go, you are too likely to pick up ripple and ridges.
Prepare the liner by cleaning/scrubbing it well. After clean wipe the liner down with gasoline or alcohol. Be sure you clean a strip at least 6" wide along both pieces of the liner you intend to put together. Make sure the liner is completely clean before you move on to any other step.
Make sure the liner is clean and dry before you start with this step. There are 2 different ways you can splice the liner. There is a "double" seam and a "single" seam. For the double seam you will need 3" wide double sided tape, 6" wide single sided tape and tape activator or primer. For the single seam you will need 6" wide single sided tape and tape activator.
For the "double" seam, lay your liners out side by side on a flat surface. Again make sure they are completely dry. Apply a thin layer of tape activator on one side of the liners you are joining. You want to cover at least the 3" area. Once applied let the primer set until it gets almost dry. It will become very tacky to the touch.
Next working in small sections peel off the backing on 1 side of the 3" tape. Be aware this tape if very sticky that is why you don't want to peel all the backing off at once. As you apply it to the liner roll it down well working out any wrinkles, bubbles or creases. Once you reach the end of the liner cut off any excess tape that will not be used.
Now you will repeat the process on the adjoining liner. You will prime again with the tape activator. Then you will need to peel the backing off the tape again work in small sections. As you peel it off lay the adjoining liner directly on top and roll down again working out bubbles, wrinkles or creases. Work slowly till you reach the end of the liner. Once the 2 sides are joined we recommend using some type of roller over the top.
Some people will choose to stop here and be done with the seam. We recommend going back over the top of the seam with the 6" single sided tape. You will clean and prime the area as described above. Then peel and stick the 6" wide singled sided tape down the center of the seam. Again roll down the seam with some type of roller in order to create a good seal and work out bubbles.
If you choose to do the single seam you will need the 6" wide tape and tape activator. Before you begin the actual seam make sure you follow the cleaning instructions listed above. Once liner clean and dry, slightly overlap the liners that will be joined.
Apply a thin layer of tape activator being sure to cover at least 3" on each liner. You will center the tape down the middle of the seam.
Once the primer is tacky/almost dry, you will peel backing off of the tape and apply tape to the liners. Center the tape so that you are covering approximately 3" on each liner. Work in small sections.
Once you have applied the tape to the entire seam, roll down the seam with a roller working out any wrinkles, bubbles or creases.