Calcium Hardness and vinly liner "stretch"

[lances4803]

Went by the pool store for a free test (I have a full set at home, but like to see what they come up with).
I was informed that my calcium hardness was very low, at 50. (It has traditionally always been 60 to 80.)
I told him a calcium hardness in a vinly pool is inconsequential, and they said it affects the vinyl liner. That a vinyl liner should last 10 to 15 years, but with low calcium hardness it will only last 5 years.

Anyone heard of this?

 

[waste]

I've heard something similar, but I don't believe it

 

[woodyp]

It affects their sales of calcium a whole lot more.

 

[JasonLion]

There have been quite a large number of people running their vinyl liner pools at very low CH levels for years and years. If it actually reduced the lifetime to only five years that would have been obvious long before now. No such effect is observed.

 

[lances4803]

That is what I thought.
I read all the old posts about water quality, water feel, chemical balancing, etc.
Vinyl stretching was a new one.
Thanks much.

 

[chem geek]

There was a brief technical discussion about this in the latter part of this thread. In practice, there are many people with 10-15 year liners who have had low CH with no issues. For sure, the average life isn't reduced to 5 years.

Next time you go back to the pool store, find out where they got this information. Then you can trace back from there until you either get to 1) a definitive scientific peer-reviewed paper on this issue or 2) someone who carried out specific experiments on this issue or 3) someone who has kept a log or done a survey of a large number of pools correlating CH level with vinyl life. Most likely, you'll find that someone way back when just assumed that the CH needed to protect plaster pools is needed for vinyl as well and everyone has just been repeating this misinformation ever since. As you'll see from the thread I linked to, some of the vinyl manufacturers themselves tend to quote the same CH ranges as for plaster pools, but without any scientific explanation or supporting data.

This same sort of thing happened with the "10x rule" for breakpoint chlorination where it was misapplied to Combined Chlorine (CC). In this case, even chemists at chemical companies were sucked into this fallacy. People in this industry tend to repeat "conventional wisdom" without questioning it and getting to the core science or to actual field observations. Now in the case with CH for vinyl pools I can't be as definitive as with the "10x rule" since the latter was clearly wrong and is demonstrated by basic science. The CH for vinyl pools is more complicated than that, requiring field observations in addition to knowledge of the chemistry.