Before you take it apart and replace the seal, try this. Sometimes the ball gets out of round just a smidge and the seal doesn't seat properly. With a gloved hand, reach down and hold the ball while you also (gently) begin to flush (don't let the ball rotate with the flushing motion for just the beginning of the flushing motion.) Perhaps this will realign the seal. IF not, then proceed with seal replacement. Blessings