Safe pH levels for vinyl pools

[chem geek]

The study went from a PH of 2-10 and said that it gets progressively more likely below 7 however other factors contribute ... these other factors such as high cl with no or low CYA are routinely recommended here with no qualification.

We don't recommend no or low CYA with high FC (chlorine) here so I don't understand this statement. The active chlorine (hypochlorous acid) level recommended here (see Best Guess Chlorine Chart) for normal chlorination (FC that is 7.5% to 15% of the CYA level) is the same as found in a pool with 0.07 to 0.14 ppm FC with no CYA while the level for shocking (roughly an FC that is 40% of the CYA level) is the same as found in a pool with 0.6 ppm FC with no CYA. This is based on known equilibrium chemistry described in this paper, and computed in this spreadsheet, and validated by pathogen kill times, oxidation rates and ORP as described in the "Chlorine/CYA Relationship" section of this post and also validated by the tens of thousands of pools on this and other forums that have algae growth prevented by following the chlorine/CYA relationship.

Also note this info:

Then we have fillers. Calcium carbonate is often used as a filler in plastics. Depending on the amount used in a blend, calcium carbonate can increase the modulus, increase the hardness and at very high loadings decrease the cost of the formulation. It was found that at levels less than 7% by weight the physical properties were not significantly affected and that, at levels over 20%, the physical properties were compromised and the chemical resistance severely compromised.

Stanford et al. (1979) showed that high filler loadings resulted in excessive weight gain and, thus, poor chemical resistance. A PVC formulation incorporating high calcium carbonate amount is by far the most significant negative factor in acidic leachate environments. When exposed to acidic leachates, and with 37% HCl, formulations with less than 7% calcium carbonate, incorporating a branched or linear phthalate, had less than 5% weight change and – more importantly – were still very flexible.
:
Calcium carbonate filler loadings of greater than 7% should be avoided in low pH (acidic) environments.

It would be good to know if all vinyl pool liner manufacturers used less than 7% calcium carbonate in their formulations. Maybe some don't and has led to the idea that low pH can be harmful to even the integrity of vinyl pool liners.

[waterbear]

Then don't. We'll take care of it.

Carl

I am sure he will find a happy home at TFP.

[PoolDoc]

I am sure he will find a happy home at TFP.

There's nothing like giving your competitor your mostest favoritest customers!

[CarlD]

There's nothing like giving your competitor your mostest favoritest customers!

"Martin! Your customer!" -- Hugh Grant, "Notting Hill"