Our pool is about 5 years old and this year the liner feels like the walks are covered with sandpaper. Water is sparkling clear, it is an L-shaped inground pool. 2HP pump that was just replaced this year. Dimensions are 16 x 36 x 43. It's only on the walks and steps, the bottom is fine. Pool is a saltwater pool so chlorine isn't measured the same way. Any advise???? Thanks!