Safe pH levels for vinyl pools

[PoolDoc]

It began where it shouldn't have, in the middle of a poster's questions about how to get his pool ready for vacation.

Is that article available online? If not, do you have a copy you can email me (poolforum AT gmail DOT com)? Who is Don Redpath?

Ben

[giroup01]

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

Basically if the liner is discolored it means too much chlorine, if it's wrinkled it means pH too low. pH is what kills liners. The calcium content is dissolved and the liner swells up and wrinkles. Water with high chlorine concentration can then penetrate further into the liner. The liner loses its elasticity, it elongates etc, we've all seen it.

[PoolDoc]

Actually, according to two different engineers -- 10+ years apart -- at Canadian General, the calcium content is mostly irrelevant. But, the swelling at low pH is consistent from all sources.

However, what you are saying about chlorine penetrating is also contradicted by all vinyl engineers I've spoken with -- the consensus I've encountered is that chlorine at pool levels (<100ppm) doesn't affect the vinyl sheeting, but CAN damage the printed patterns, and some dyes, especially medium blue.

Also, the article refers to a study, but doesn't cite it or state when and where it took place nor who conducted it. Nor is there any bio or CV info on "Donald Redpath". The article reads much like one of the "expert" articles from Service Industry News . . . and those aren't entirely trustworthy.

So, unless there's better info, I'm going to stick with the info Chem_Geek and I have been given by vinyl sheet mfg engineers.

Ben

[giroup01]

I'm saying that once the vinyl swells up, it becomes more porous and can absorb chlorine more deeply into the layers.
But it doesn't matter really. The Europeans have really researched this, my info is from AFNOR documents and internal documents from the manufacturers over there. There may exist some differences in the manufacturing between the continents.

[SalemCastles]

So the real context of the discussion is are you being alarmists? I think most definitely you are. So I believe Carl is right when he suggests this forum is not for me. I quoted below to illustrate according to Ben just a few months ago that the engineer said a of PH 5-9 is ok. But what does the manufacturer know. 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. At the end of the day it's just a swimming pool. In all cases the function of the liner was never compromised ... saying you have to do this or that right now or you WILL damage this or that is just (with due respect) a way to raise your self importance. I do have a last question ..how do I delete my account?

http://www.poolforum.com/pf2/showthr...yl-Pool-Liners

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

[CarlD]

I do have a last question ..how do I delete my account?

I'm sure Ben will be able to accomodate you.

We have acceptable ways of challenging our pre-conceived and previously demonstrated premises, and unacceptable ways. It is as simple as that.
Several have been challenged, and challenged successfully. But how you challenge is what matters.

Good luck to you.


Carl

[giroup01]

DurhamHouses,

Keep in mind that these are pool forums aimed at residential pool owners, little self-help communities. There is a definite "dynamic" that exists within these forums. I think it was PoolDoc, in an earlier version of this board, that said "As I rule I'm right and you're wrong." The underlying aspect, the common ground in all of them is that the participants don't know what they don't know. From that starting point discussions can go anywhere.

At the end of the day it's just a forum.

I can have a graph by one of the manufacturers that shows the absorption of water by a liner as a function of pH over time:



But then you'll have somebody come along and question it, or say it ain't valid for whatever reason, without any background knowledge or knowing the context.

Then a decision is made, like what just happened, to favor another bit of information, or another source, hence the information is never complete, and that decision forms the basis for what now becomes the accepted answer, the "truth".

Like I said, it doesn't matter, really. It's the nature of forums. Just let it go.

[PoolDoc]

Durham, you are overlooking a key point: when people test pH 6.8 or 7.0, that does NOT (depending on their testor) mean that the pH is 6.8 or 7.0. Rather it means that their pH is 6.8 (or &.0) OR BELOW.

The reason is, their testors only go to 6.8 or 7.0, so they read any result that is that yellow OR yellower as the low value on their kit.

You made two mistakes.

Your first was to overlook the fact that the pool had not been 7.2 and then drifted down to 7.0. Rather it had been largely untested, which means that none of the moderators really knew what the pH was: for all they knew, it WAS 5.0, because that pH level would have produced the SAME reading -- for many pool owners, using many of the standard kits -- as if it was actually 6.8 or 7.0.

Now, I'm not sure that everyone who posted understood WHY it is important to get the pH above 7.2, or that an ACTUAL pH of 6.8 is not damaging to liners. But, the bottom line is, whether they understood or not, THEIR advice was operationally correct and yours was wrong . . . because neither you nor they could be sure the the OP's pH was NOT 5.0, until they raised the pH to the mid-range of their tester!

Your second mistake was in challenging the moderators in the middle of a post, rather than here.

The advice given here is not perfect. I'm aware of many flaws in some of the posts, including some of mine. But the fact is, the advice given here is, all things considered, probably the best advice a residential pool owner can obtain on operating their pool effectively and economically.

But . . . it only works, when people follow it. And when someone challenges the moderators mid-stream, what users tend to do, is not wade through all the complexity of the various points in the argument, but rather they retreat to a what is familiar and thus psychologically more comfortable: pool store advice.

So, not only was your advice wrong in its substance (if not in all the reasoning behind it) but also your challenge in the form you presented it likely to result in the OP bailing out and proceeding to follow even WORSE advice.

I'm not sure whether you belong here or not.

Once you transition from asking questions, to posting answers, our expectations of your behavior go up considerably. We have an area for public debate, that's been heavily used over the years. But that place is NOT in the middle of threads from someone about to go on vacation.

So, if you feel yourself unable to offer my moderators the respect they've earned from 10 years of trying to help 1000's of people, by bringing your challenges to the right section and posing them with a polite and careful manner . . . then I agree, the PoolForum is not for you. There is no shortage of forums where rudeness and disorder are the norm.

Sincerely,

Ben Powell

[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.