Calcium Hardness (CH) for Vinyl Pool Liners

[CarlD]

Hi Richard,
I don't track TFP's stuff at all so I wouldn't know. I think the other mods have a similar experience to mine, and I know Al and Lisa have vinyl liners. I'm 99% sure Jan does too, and we all never bother with calcium levels. Al's liner has got to be close to 15 years old, too.

You'll need about 15 data points before you can legitimately determine a statistical trend--too much noise below that.

Meanwhile, don't you have a scrap of liner around you can grind up and test for calcium carbonate? Give me a couple of more years and I may be able to give you mine!

Carl

[aylad]

My liner was 9 years old when I had to replace it, and the original rips that caused the need for replacement were well above the waterline, not below....

The calcium in our fill water is less than 20 ppm and I think I might have used cal-hypo for chlorination 4 times in that 9 years, in a pinch when I was out of bleach. So you can add that one to the count...

Janet

[PoolDoc]

Hi Richard, All;

Richard, if you can dig to the bottom of this, it would be very helpful to many. I did some work on it years ago, but ran into problems and gave it up. A lot of my info came from a product engineer at Canadian General (http://www.cgtower.com/). At that time (15 years ago), they were making a big part of the PVC sheeting used by US liner mfgs.

What I learned from him was the following:
+ calcium carbonate is used as filler in some, but not all (he thought) sheet.
+ low calcium was not (he thought, supported by some casual testing) going to cause premature failure.
+ like other flexible PVCs, vinyl sheet is a mixture of PVC, plasticizers, UV stabilizers, colorant, filler, and ??
+ there is no standard formulation.
+ liner color may, or may not, be in the sheet.
+ liner patterns are printed on by the liner mfg.
+ at that time (as I recall) he thought that NONE of the liner mfgs were sheet mfgs.
+ there were 2 or 3 mfgs of sheet.
+ sheet formulation was proprietary and varied from company to company, but also from time to time.
+ the same model & weight of liner might be actually made from 3 or 4 different instances of sheeting, each with different composition and properties.
+ many of the liner mfg did not understand the intricacies of PVC mfg, and thus did not understand what they were buying. There particular concerns often focused on manufacturing properties, like print-ability and suitability for their equipment.
+ printing ink varies too, and there's no guarantee that the ink for a particular model is the same over time.
+ generally, low pH tended cause plasticizer leach-out, but he didn't have data tying time and pH to damage.

Bottom line for me: there was no way to tell from one liner to another, or even from one liner today to the same liner tomorrow, and thus there was no valid way to get very specific about what would affect which liner in what way. Even with the minimal exposure to liner pools I've had, I've seen big differences in liner life expectancy in similarly managed pools.

Ben

[PoolDoc]

Whoop! Whoop! Whoop!

CGT is now making finished sheeting and has a BUNCH of tech data:
http://www.cgtpoolliners.com/cgt-technical-manual.htm

I'll archive copies, but don't have time to read it all now.

Ben

The content in this one will be particularly of interest:
http://www.cgtpoolliners.com/cgt-tec...bulletin-4.htm

(I lied; I've ended up reading quite a bit as I archived. A lot of the data dates to 2007)

[PoolDoc]

Ok, I got side-tracked, and called CGT. I'm ADD and eternally curious; whaddya expect?

Spoke to a liner product engineer, "Immanual + foreign last name" -- it bugged him that I couldn't understand his name, I so I gave up. After we spoke for awhile, he transferred me to "Carl Flieler" (sp?) => Carl Flee-ler who is the pool liner guy, but he wasn't in.

Anyhow:

+ OK pH range is 5 - 9
+ The idea of adding calcium carbonate scared him, because he said high pH is more damaging than low pH.
+ There are definitely variations in liner material quality, and there is imported knock-off material. But he thought the patterns (see website) are likely to indicate source fairly well.

Richard, you might want to talk to 'Flee-ler'.

Ben

[giroup01]

http://piscines-apollo.com/docs/chemicals_and_vinyl.pdf

[chem geek]

Ben,

Thanks for those links. This one says under "Calcium Hardness Check", "Calcium levels should be kept at a minimum level of 200 ppm to avoid corrosive conditions. Calcium levels over 500 ppm may cause problems such as cloudy water or scaling on the liner surface." (this link also says CH should be a minimum of 200 ppm). Of course, the "corrosive conditions" they are talking about are the ones people refer to for metal corrosion if there isn't a thin coating of calcium carbonate and that's a debatable and controversial topic (see this link for one such discussion) and they say nothing about low calcium doing anything specifically to the liner itself. Other CGT links refer to low pH being the real culprit along with very high chlorine level such as found by placing a Trichlor puck on vinyl (which is also low pH). They recommend using Cyanuric Acid, which as we know will reduce active chlorine level so reduce the effects of bleaching for the medium blue that is apparently the only one affected by chlorine.

The link from giroup01 (thanks for that) says the CH should be a minimum of 100 ppm. However, the lab studies looking at different water parameters found that low and high pH were the most problematic while high chlorine levels could fade vinyl and also accelerate the effects of low pH. The ideal pH was between 7.0 and 7.5. Below 7.0 there was in increase in wrinkling, loss of tensile strength, elongation and fading. Above 7.6, the vinyl loses weight and expands. As for chlorine, it should be noted that they had a starting CYA level of 100 ppm which is rather high. The FC of 20 ppm in these conditions adversely affected the vinyl (interestingly, this is only an active chlorine level of somewhere between 0.1 and 0.4 with equivalent FC with no CYA of 0.2 to 0.8 so not really that high and we've had people shock with an FC that is up to 40% of the CYA level without bleaching liners, so I don't know why they saw that unless the chlorine test didn't have CYA the way their pH test did). Unfortunately, they did not test for varying CH, but since their tests were at a CH of 100, that at least doesn't seem to be a problem level in the short-run.

Richard

[CarlD]

It's beginning to look like empirical evidence from users may be the proper foundation of a test protocol. But there has to be a quantifiable way to measure damage to the liner, compared in a double-blind setup.
In other words, you first have to model a behavior/reaction and then control conditions and have a viable measurement methodology.

Guess I've been in clinical trials programming too long!

Carl