Calcium in vinyl pools

Canucklehead · Aug 1, 2023

Hey all. The pool has been looking great this year, which is why I haven't checked in here for a while.

TFP recently released a memo that, among other things, says that the ideal Calcium level for an in-ground vinyl pool is 50-550, while 0 to 650 is "acceptable."

I stopped testing for Calcium Hardness, and stopped adding Calcium Chloride, when I joined TFP and was advised that there's no need, in a vinyl pool. That it's a concern with plaster pools, but not vinyl.

Is there a compelling reason why I should raise the Ca level to the "ideal range"?

Thanks!

Newdude · Aug 1, 2023

Canucklehead said:
Is there a compelling reason why I should raise the Ca level to the "ideal range"?

Legend has it that liners once used calcium as a filler. In theory the water would leech CH from the liner the same way low CH water does to plaster.

It probably wasn't ever a thing because the industry sure loves applying principles where they don't belong, but it's definitely no longer a thing.

Mdragger88 · Aug 1, 2023

Do you have a heater?

Calcium Hardness - Further Reading

www.troublefreepool.com

Newdude · Aug 1, 2023

Mdragger88 said:
Do you have a heater?

PERFECT example of the industry applying something where it doesn't belong. Like the 100 year old steam boiler reccomendation for CH, which is nothing like a pool heater.

*sigh* but for warranty purposes we have to follow it when applicable.

JoyfulNoise · Aug 1, 2023

Liners do use calcium carbonate for multiple reasons - it’s a colorant (white) that is cheaper than all the alternatives and it promotes certain mechanical and rheological properties during the manufacturing process. However, there are probably a dozen different high volume PVC sheet manufacturers in the world and all of them maintain their own “secret sauce” recipe for the “Best PVC Film EVAH!!!!11!1!11!” And so, none of them will tell you how much carbonate they use and none of them will tell you if calcium leeching affects their products because “it’s the best PVC film material ever and why would you want to know such silly nonsense you feckless rube!!!” Add to that the fact that pool liner manufacturers will source their starting materials from any one or all of those worldwide suppliers and they will construct a liner from material from different vendors, and you have no way of knowing what effect water saturation will have on a liner.

It’s just not worth worrying about. Use CH for heater warranty needs and for foam inhibiting properties.

Canucklehead · Aug 2, 2023

We do have a heater finally, installed this summer.

So I should add Calcium chloride if I have foaming issues (which I don't) but also because the heater manufacturer , I now realize, tells me that 200-400ppm is recommended, to avoid corrosion! My current level is 10ppm. Off to the pool shop...

Thanks everyone. You all make pool management fun and easy, not to mention understandable.

JoyfulNoise · Aug 2, 2023

Just add the calcium slowly in small batches. If you add CH increaser all at once it will not dissolve fast enough and your water will go cloudy due to unmixed regions of very high CH. Also, calcium chloride granules heat up a lot in water as they dissolve. You don’t want hot little grains of calcium sitting on the liner. So premix small amounts in a gallon buck of water and then add that slowly in front of a return. You can take several days to increase your CH and measure as you go so you don’t overshoot the target.

Mdragger88 · Aug 2, 2023

What is your fill water ch? That will add to your ch over time as well.
I would go with 200ppm as a target goal to satisfy your heater requirements - small batches to get there as Matt suggested.
Btw - you can purchase calcium chloride at other places besides the pool store just be sure to check the label/msds so you know what you’re getting.