Still Confused CH & Vinyl Pools with fiberglass stairs

[swomacks]

Hi all! I am sorry if this is getting way redundant. I have read several threads on the subject and still haven't determined if TFP Experts or anyone for that matter has definitively answered the question. My 24ft vinyl above ground pool with fiberglass stairs has a calcium hardness of 50ppm. I have been adding in small portions driveway heat in an attempt to raise the level. So far there is no change. Should I add more or leave it alone??? Thanks for any response.

 

[Pool Tool]

CH is not required in a vinyl pool. The 50 ppm minimum sometimes referenced is for CSI considerations. Save the driveway heat for the winter...if it snows

 

[pooldv]

That is right. But, if it makes you feel better raise it to 150 ppm. It won't hurt anything.

 

[dlaslo]

Once in a while I take a sample of water to the pool store and get it analyzed...mostly for metals. Every time they tell me I should have 200-500 ppm CH for my vinyl pool and I ask why and she tells me to save the liner and to prevent the ring around the top at water level. They are using a commercial software called ClearCare Expert. I followed their advice the first time but ignored them ever since. She sounded pretty convincing this time.

 

[Mr Bruce]

She's a good salesperson you say? Do you know who I would trust more: Chem Geek/JoyfulNoise/Dave vs somebody that is trying to separate me from my money

 

[Divin Dave]

Hi dlaslo,
Plaster pools aboslutely require proper CH levels.
Vinyl Pools do not.

the people at the pool store dont know the chemistry and their computer and reference sheet does not differentiate between types of pools. Their main goal is to sell you something, whether you actually need it or not.

TFP has listed the recommended levels (and tons of other stuff) in Pool School. It would benefit you to click the button and learn more about pool chemistry and where to find TFP recommendations.
Pool School - ABCs of Pool Water Chemistry

Below are recommended levels. As you can see, the CH level for a vinyl pool is 0-300
Pool School - Recommended Levels

I hope this definitively answers your question.

 

[dlaslo]

Hi dlaslo,
Plaster pools aboslutely require proper CH levels.
Vinyl Pools do not.

I hope this definitively answers your question.

Yep...that's what I understood as well. (i've been around here for a year now). There is some controversy on this (I first thought calcium was used to improve the langlier index - but that's not the case)

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(ChemGeek) Re: Did you know that Vinyl liners contain calcium?

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.
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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..​

I'm a chemical engineer and before I retired I worked in the flue gas desulfurization field. We neutralized the acid gases with a calcium carbonate slurry and checked chemical resistance to a whole gambit of construction materials coming in contact with this environment. The use of calcium carbonate fillers in plastics and especially rubber raised red flags with me and logically I thought it would be a major problem (although we were always saturated with calcium, there was the acid, of course). But it never seemed to be a problem.

And indeed, a quick check of resistance properties of vinyl shows it is OK with saltwater, distilled water (zero calcium), dilute sulfuric acid !!!, but interestingly, not calcium chloride.b Funny that calcium chloride would REDUCE the solubility of calcium carbonate (common ion effect).....so that's interesting.

But I'm not convinced that all pool stores are selling pool chemicals just to make a buck. There probably is at least an intuition that something may happen in the life of a 10 year warranty - and maybe even data - but probably a weak effect. I think I may call the vinyl liner manufacturer next week!!






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[Divin Dave]

dlaslo,
TFP recommendations are based upon scientific principles and chemistry that have been verified.
To date, (at at least to my personal knowledge) there isn't any valid scientific data that has been found that would lead us to believe that x level of CH is required in vinyl pools.

Obviously there will probably be those few who disagree, however we here at TFP respect their opinion and comments. We are always open to adjusting our recommendations should conclusive data show that a vinyl liner pool CH level should be maintained to a tighter range than is stated in the TFP recommended levels.

 

[needsajet]

The OP has fiberglass stairs, and if they also have metals in their water, the risk of metal stains can be reduced by raising calcium hardness.

I also found past discussion of blistering risk on fiberglass from low CH, but that risk was only tenuously supported by a conversation with one engineer at a gelcoat company.

Pool math has a separate selection for fiberglass which includes a 220 PPM minimum for CH