and low calcium causes them to become brittle! Or at least I was just told when I went to pick up some 12% bleach at the pool store. He was told by his "chemist friend" and even drew out the basic formula for vinyl CH=CH2 to show me all the calcium (CH). I tried to explain what a hydrocarbon was but got quite a perplexed look. We ended up agreeing to disagree and I left with no calcium. I told him to look on the bright side, if he's right they will get to replace my liner that much sooner.

They've never quit trying to sell me calcium for my vinyl liner pool.....................just because their testing equipment says "to add some". You get some really strange looks when you ask them.........."Why?"
And my adding plain old bleach will cause my liner "not to last the normal 15 years or so." Told them my wife would want to "redecorate" before then anyhow!

We should come up with some cool T-shirts

"WARNING - Trouble Free Pool School Graduate"

That is so wrong on so many levels, it's laughable. As you pointed out, "CH" is a carbon and a hydrogen and has nothing to do with calcium hardness. Vinyl itself is a polymer formed from vinyl groups which is what he was showing (which is actually -CH=CH₂ since it's a chemical group, not a standalone chemical) and the polymer known as vinyl doesn't actually have any vinyl groups itself -- the double bonds are all gone since they are what open up to form the polymer.

Polyvinyl chloride (PVC) is a polymer of groups that look like [-CHCl-CH₂-]_n which consists of carbon, hydrogen, and chlorine. There are other chemicals added for vinyl liners such as heat stabilizers, UV stabilizers and plasticizers (which is what makes vinyl soft). The plasticizers are complex chemicals (usually phthalates such as dioctyl phthalate, DOP, see here) composed of carbon, hydrogen and oxygen. The UV stabilizers are typically a benzophenone which is composed of carbon, hydrogen and oxygen. The heat stabilizers are typically a barium/zinc-alkyl phosphite which consists of barium or zinc, carbon, hydrogen, oxygen and phosphorous.

No calcium to be found!

chem geek. I understood everything right up until 'laughable'.
But I'll take your word for it....lol

I think that you are missing the little-known secret of the actual process, and the conspiracy that endeavors to keep it from you...

The feedstock that is used in the production of vinyl liners comes directly from the middle range of fractions distilled during the calcium refinement process once the calcium is taken from the calcium well by the calcium drilling/pumping platform. Once these lighter calcium fracs are distilled off, they can be used for many many things, depending upon the amounts and mixtures of other calcium that is added to make them more or less calcium. Once calcium stabilizers and calcifiers are added, the vinyl liner pretty much just 'pops' out of the mixing rollers, needing only a light dusting of calcium to make it ready for the market, otherwise the aggressive nature of the calcium would leech additional calcium from the atmosphere, ultimately leading to a situation that theoretical scientists have called "calcium-deficient atmosphere", a condition under which the vast majority of the earth's calcium is assimilated by the air in an attempt to satisfy the reduction by the vinyl being produced. It is the ultimate virtual doomsday potential of this production process that makes everyone try to convince you that it is all done with hydrocarbons.

I hope like crazy that was a joke! If not, you've just matched Richard in the ability to confound me, using words I know.

Wow, this got complex fast. I'm reminded of a quote:

"My cat's breath smells like cat food." -Ralph Wiggum

Calcium carbonate is used as a filler in PVC formulations.

http://www.specialtyminerals.com/filead ... %20bro.pdf

http://books.google.com/books?id=8j3elW ... CBsQ6AEwAA

I remember reading an AFNOR bulletin stating the content was 4% or thereabout in pool liners.

what-is-the-effect-of-low-ph-levels-t24369.html :

"Putting aside the chemistry and water balance aspects, the low pH could possibly damage a liner by causing wrinkles, hardening and elongation. This is partly due to the acid dissolving the calcium carbonate used as a filler in PVC formulations. Elongation then allows the disinfectant to further penetrate the membrane possibly leading to discoloration."

waste, Ohm_Boy is being facetious.

CaOCl2, those references refer to calcium carbonate filler in rigid PVC. Since vinyl liners have plasticizers to make them softer, I doubt that calcium carbonate is added to them since that would tend to make them stiffer/harder. [EDIT] I am wrong about this -- see later posts below. [END-EDIT] This AFNOR standard may be what you are referring to indicating a small amount of calcium carbonate filler in vinyl liners, but I'd appreciate it if you could verify that (if you have that bulletin).

I don't know if 4% calcium carbonate in vinyl (PVC) would need water to be saturated with calcium carbonate because the forces that hold it in the liner are probably not like plaster where it is physically integrated in much larger quantities.

We do know that low pH is harmful for vinyl liners (especially from Trichlor pucks touching liners which are both low in pH and high in chlorine), but we haven't had any reports of any issues from low CH levels.

OMG! I am SO sorry.
Yes, I was being facetious.
I really have never seen a calcium well, a calcium well drilling platform, nor a calcium refinery distillation stack. There is NO calcium refinery in Texas City.

James,

The manufacturers quoting the same standard water balance parameters isn't so relevant since some of these same guys also claimed that bleach shouldn't be used (though some to say chlorinating liquid is OK) so their credibility is a bit suspect. However, as far as an additive/filler, it's clear from your references that granulated calcium carbonate is often used. So the question is whether water that is not saturated with calcium carbonate attacks it or whether it is sufficiently embedded into the vinyl for there not to be a problem as compared to plaster pools that clearly have large areas of calcium carbonate directly exposed to the water.

I wonder if there some sort of experiment that could be done, perhaps at hot water temperature to accelerate the process, with vinyl samples exposed to buffered water with virtually no CH vs. water saturated with calcium carbonate, both at a pH of around 7.5. We might then see if there is any difference in elasticity, coloration, folds, or other effects. We could also see if the CH and pH rise in the no-CH water vs. the saturated water which would imply leeching and dissolving of calcium carbonate from the vinyl. We've never had any reports of people seeing unusual pH or CH rises in vinyl pools, but then again most aren't checking their CH levels.

There is also a secondary question, if the calcium is removed what happens? Does it actually damage the vinyl in any way? The primary risk for vinyl liners seems to be either loss or destruction of the plasticizers, which I imagine has little to do with the calcium filler.

We have what is probably tens of thousands of pool years of very low CSI in vinyl liner pools with essentially no complaints at all. So I can't imagine that anything is actually going on here. Our data collection is haphazard, so we can't rule out small effects, but if there was a large effect we would have heard about it by now.

I'll be the guinea pig. We have almost no calcium in our water and our fill water has zero (less than 20ppm). The pool will get real close to zero during the season because we average 60" of rain a year here and are not adding any back to it. However it may take 10 years or so for the results!

(probably should be split to The Deep End)

Jason, while I don't know the chemistry like the others - I like your line of thinking on this. If it happened (the cal being leached from the liner), wouldn't chlorine be leached from PVC, if the cl levels got low?


Dave (Bama), you're a brave man I didn't keep 'scientific' track of the liner pools I didn't add any calcium to, nor check the CH levels, but acidic water was always present in heat exchanger failures and brittle 'new' liners.

Thanks for moving this to The Deep End where this discussion really belongs.

I ran into some sources that shed some additional light on this calcium carbonate in vinyl issue. This link says the following:


This is consistent with what I wrote earlier that I thought that higher levels of calcium carbonate would be counter to the goal of having more flexible vinyl so that implies that the level of calcium carbonate is probably kept lower in vinyl pool liners.

Then there is this link which has the following very interesting information:


So as long as the amount of calcium carbonate in vinyl is low (< 7%), it seems that even acidic conditions don't cause serious problems. The implication here is that low CH levels may not be an issue with these low levels of calcium carbonate.

We may never know for sure about this issue, but at least we've got more info to ponder.