Potential Vinyl liner damage if converting from Bacquacil to Chlorine in 20 yr liner ? Liner appears in very good shape after all these yrs using Bacquacil . Dont want to start problem where none exists on liner, but typical baqua issues have me thinking of change . Holding at 15 ppms FC until residual baqua is gone sounds pretty hot, potentially damaging ? Generally when I open in the spring I shock with only 2 gallons of Liquid Chlorine , residual Bacqua may be as low as 2ppms . I do that to help fast kill any algae water mold present. Usually turns water yellow for about 2days then cloudy then as it clears and chlorine is used up . I shock with hydro peroxide this process takes about a week to get very clear water. Sand filter does load up often with Baquacil and dull water does happen occasionally . Mustard algae does also appear after hottest part of the season . Considering the cost of more frequent liner replacement what have you saved in costs if thats the primary even secondary reason to convert to labor intensive ( my opinion) monitoring of of a chlorinated pool ? I can let Bacquacil pool go for days without testing and residual is still in specs. Still a season or two with chlorine may be the way for me . Just my thoughts . To me the liner is key here