You guys are gonna love this...

[mwsmith2]

I can understand how there is need for some calcium in the pool for the pump...i'm just not exactly sure how the liner needs it too.

Michael

[gregugadawg]

nah i wouldnt necessarily say the liner needs it, I am just in atlanta here and the ch out of the tap is 80 ppm, i tend to get it to about 250 in a gunite pool, 150 for vinyl and fiberglass and 150 for spas. I wouldn't say it affects the liner but I did look on some major manufacturers of liners and they said to keep it 100-200. I know most places in the country arent gonna be 50-80 out of the tap like we are here.

[mwsmith2]

I do remember now Ben saying at one time that certain liners require a small bit of calcium in the water. I also did do a bit of playing around with the langelier saturation index, and if you subscribe that it's correct, it's impossible to stay out of the corrosive range without any Ca in the water. It seems that 100 - 150 is the range that keeps the index happy. I haven't researched it really all that hard, but I think i'm going to hit up some mechanical and chemical engineers at work tomorrow and see what they have to say.

Michael

[CarlD]

Greg,
Please explain to me how water without calcium is corrosive, but water with calcium is not.

I understand how high salt levels can be corrosive, how non-neutral pH can be be corrosive and how too much chlorine can be corrosive.

I also understand how a leechable chemical that is present in one environment, like the calcium in concrete or plaster pools will be dissolved by water that lacks calcium. Therefore calcium in the water presents a saturation to prevent it dissolving from the concrete or plaster.

But please explain to me how the vinyl will be damaged by low calcium if the other chemicals in the water are balanced? Exactly what elements react with the vinyl and how does the calcium prevent it?

Oh, and I keep my water VERY light on calcium and have YET to require a pump seal.

Oh, and by the way, I'm moving this thread to the China Shop.