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Ok so what I get is if the water stays clear, doesn't smell, I'm not getting any odd feeling on the inside surface( slimy or rough) and I'm not getting any abhorrent skin reactions, then things should be fine. In truth, this was a very inexpensive tub when we bought it 20 some years ago and I would've expected it to spring a leak somewhere long before now but it seems to be holding up so far. I do remember when my wife was handling the additives that when we turned on the high pump if I got a whiff off the water it would take my breath away. Very gaseous. Really made it feel like an un-healthy atmosphere. Really cuts down on the enjoyment factor. What I'm doing now seems to be working so I guess I will carry on until something comes up that tells me changes are in order. Thanks for the information.Robert