Have a small rip in your vinyl liner. You can repair it – no problem. AND you don’t need to drain the water, actually you don’t want to drain the water as you risk damaging the liner further.
Simply purchase a repair kit. Measure the tear in the liner, make a round or oval patch (no squares or rectangles) and apply a generous amount of glue to the patch. Fold the patch in half, (glue to glue) until you are ready to place on tear. Open patch under water and place the patch on the tear, hold for minimum of one minute. You can place the vacuum over the patch or something heavy that won’t do further damage to the liner to add weight until the glue sets. Voila, liner repaired.