The first thing you will need to do is to make sure the entire area around the torn pool liner is scrubbed and completely clean. It is important to remove all algae or dirt so that the patch and the adhesive will have a clean surface to adhere to. After the area is thoroughly clean, push the seam of the pool liner completely flat and check that there are no wrinkles. At this point you should probably put on a pair of disposable latex gloves to protect your hands from the glue that will be applied later.
Using an exact-o knife or scissors carefully cut a rectangular piece of vinyl from the patch material making sure that it is about 4 inches wider and longer than the total size of the rip in the seam of your pool liner. You will want to make sure that the corners are rounded on the vinyl patch you just created because it will conform better to the tear in the pool liner seam. Take a stick or some sort of spreading tool and put the glue all over one side of the vinyl patch. Make sure the glue is both in the middle and around all the edges so that every part of the patch will stick to the pool liner.
Take the side of the patch with the glue on it and center it over the leak in the pool liner. Press down hard and hold for about 60 seconds making sure that the edges of the patch are completely stuck to the pool liner. Smooth out any wrinkles or bubbles underneath the patch and check to see that the patch conforms to the outline of the seam in the pool liner. After you stop holding the patch the surrounding pressure of all the water in the pool will act as an aid for holding the patch in place. It is important to remember not to touch or bump into the patch for a full 24 hours to make sure that it forms a tight and permanent seal.
This is a cheap and easy way for anyone to patch a pool liner on the seam. This method does not take very long and can save you hundreds of dollars in the long run. If ever your pool liner springs another leak you can repeat this process as many times as necessary.