Shouldl water chemistry be the same for all type pools?

[Tishabiondy@natlmail.com]

Sorry if this is kind of a silly question, but could someone please tell me what I should keep all of my numbers at in a fiberglass pool? I have a Taylor test kit and try to keep those recommended numbers, but now I wonder if fiberglass has some different requirements. Thanks.

Tisha

[waterbear]

fiberglass pools have a basically non reactive surface so water balancing is a bit easier. Generally the numbers used for a plaster pool are appropriate. There is some question on how much calcium, if any is needed for fiberglass but there seems to be some evidence that maintaining at least a 150 ppm calcium hardness can help prevent staining and 'cobalt spotting' (cobalt leaching out of the gelcoat.

[Tishabiondy@natlmail.com]

Thanks, Evan. Is cobalting the same thing as blistering?

Tisha

[waterbear]

not really. cobalt staining looks like little black or dark grey dots that get bigger and sometimes have a brownish ring around them.

[CarlD]

Evan's right. Central target numbers on pools are safe on all chlorine-based pools (I know little about bromine and other non-chlorine pools).

The main reasons we tell people to follow different numbers for Calcium and Total Alkalinity on vinyl pools is:
1) Cost savings
2) Swings in measurements.

For example: a Concrete or plastered pool should have a calcium level of 200 to 400ppm

But your F/G pool needs less, and a vinyl pool doesn't really need any--so why should a vinyl pool owner spend $40 adding calcium that isn't needed?

Total Alk is touchier in concrete/plaster pools--125ppm is the max recommended level. But in vinyl (and probably in F/G) you can safely go to 180, and only at 200ppm should you ACTIVELY lower T/A.

Vinyl pools, however, are FAR more sensitive to low pH--it can damage the vinyl shortening its life. So if I had a concrete pool and pH was 6, I wouldn't worry, I'd just raise it. But in a vinyl pool I'd be dumping in boxes of Borax RIGHT NOW! (so my vinyl doesn't melt).

Finally, there's the numbers for SWGs. They aren't QUITE the same, but that's for a different thread!

[Tishabiondy@natlmail.com]

Thanks guys. I love this forum.