Doughboy Liner Damaged by Chlorine?

I don't know, but it sounds like freeze damage--at a guess.

I do tend to agree as far as freezing may be the cause since it split at its weakest point,the seam.
But I did do what the manual said as far as winterizing.Just a little confused,if I drained it and left the cap off all fall and winter there would be maybe 2 inches of water below the drain,when that freezes,wouldn't there be plenty of room for expansion?
Maybe I will leave outdoors again this year and do what you have been doing.
Moving to indoors in garage with a 2 wheel cart my have been a little to much force on the bottom side of sand filled tank at 150lbs putting pressure on the very bottom bolt that holds inner parts in place, that bolt is also right in line with the seam.
Thanks again for the info.

Of course, any water you can get out of the tank is water that cannot cause freeze damage. Moving the tank, full of sand, especially if it was cold out (cold stiffens plastic) could also have weakened the tank.

But I'm just guessing.