I read the frequently asked quest. before I posted this. I had a liner fall appart after three years and my pool lady said it was from not adding calcium. I mean the liner fell appart in my hands when I examined it after draining the pool. Of course now I add calcium all of the time trying to keep the level up. I read that vinal liners do not require calcium. I use chlorinating tabs in a floater and try and balance the waterwhich only needs occasional baking soda. jsamNC