A: To determine why your liner is too small or doesn't fit properly, review the following: (a) It is too cold. Vinyl will shrink and stiffen when the temperature is below 65 degrees. The sun will soften the vinyl making it easier to pack folds and wrinkles. (b) Your pool is out of round. (c) There should be two inches of sand or Styrofoam under the pool liner with an eight inch cove along the inside of the pool wall. Do not use coarse sand. (d) The pool may not be level. (e) The liner may have been installed unevenly. Verify that the bottom seam of the liner is centered in the pool. The liner may be pulled to one side.