Iron stain from pool salt - all or most salts have iron.

[tcat]

Make sure to let people know where that idea came from. Pool math gives recommendation of 50-90 so it’s not clear where the confusion is.

Pool math: 60-80 "ideal"
Google ai: 80-120 (most pool stores recommendation)

I think the confusion is "ideal", which depends a great deal on all other variables. Shoot for CSI of -.25? Curious what the "ideal" numbers are for those who didn't need to clean calcium from their cell.

 

[ajw22]

Pool math: 60-80 "ideal"
Google ai: 80-120 (most pool stores recommendation)

TA - Further Reading

www.troublefreepool.com

Manufacturers' TA recommendations are often 100-140 for TA, while Pool Math says 50-90 for TA.

One key difference is that the industry typically suggests using chlorine “pucks,” which are very acidic, while TFP suggests liquid chlorine or a saltwater generator, both of which tend to increase pH. The industry tends to suggest a higher TA level as this prevents crashing a user's pH level when using pucks, while our lower-level TA tends to greatly slow the rate of pH increase, thus using less acid to maintain your pool.

 

[pjt]

Is this the one you mean @pjt , which states "for water softeners"?

Yes, that's it. That salt works very well for pools.

given the numbers among us cleaning CA off cells

Maintain a slightly negative CSI (between zero and -0.3) and your scale should be minimal to none. I've been using my cell for 4 years with no cleaning and no buildup.

numbers among us injecting or otherwise adding muriatic acid regularly

You'll most likely still need MA additions, especially if your fill water has high TA (like mine). As TA approaches 50, be judicious with MA additions by adding just enough to get pH into the high 7s.

thinking more TA is better ('70, 80, 90 or higher TA')

There is an acceptable range, but higher isn't "better". TA is the least important parameter of pool chemistry. For a LC or SWCG pool, TA closer to 50 helps slow pH rise.

 

[Mdragger88]

That’s good to know.

The grey scum I experienced (had to clean it off the waterline) really turned me off to it, not the mention the mystery ingredient. Perhaps my experience was a fluke.

Has anyone confirmed that using this salt really does prevent iron stains? I’ve been using Jacks Magic Purple Stuff occasionally to ward off iron staining. It works well, but it’s getting pretty pricey. Oh, and apparently using enough Jacks magic can cause interferences with the Taylor salt test (false high readings). I found this out the hard way.

I have switched to the aqua salt myself and have had no new staining. Its $12/bag locally so not too terrible.
We shall see what the spring opening shows. I used a metal magic starting dose at opening which eliminated 95% of my staining & then monthly maintenance doses until closing. Fingers crossed

 

[Mdragger88]

@nuttyp thank you for your in depth salt analysis! Quite helpful and informative!

 

[nuttyp]

Pool math: 60-80 "ideal"
Google ai: 80-120 (most pool stores recommendation)

I think the confusion is "ideal", which depends a great deal on all other variables. Shoot for CSI of -.25? Curious what the "ideal" numbers are for those who didn't need to clean calcium from their cell.

I surely agree about the source of confusion. When I stare at the poolmath summary output for my aggregate pool (pasted below for fun) I find that recommendation somewhat in conflict with the many good, helpful, smart and experienced folks informing me, with good justification, that I should be running at the low end of that minimum range (ie 50ppm). When I'm feeling grumpy, I feel a bit poolstored about it - by my own favorite TFP forum LOL - and my own ignorance that had me adding TA and MA in a great repeating cycle, for years. In the ABC's section, the exact quote is "Appropriate levels help keep the pH in balance (50 to 90ppm, sometimes higher). High levels can cause pH to rise". Which also led me to the repeating cycle of TA/MA. I would have never guessed that I should go with the minimum, even though I did of course realize that my PH always rose fastest after raising TA.

In one sense I'm tempted to suggest a caveat be placed in those TA sections, stating something like "there are occasions when the low end of the TA range (~50) should be followed, especially if you find yourself regularly adding muriatic acid to keep the PH down." Something along those lines maybe? On the other hand I can understand a conservative approach because the last thing you want is puck users crashing their PH to highly acidic values that destroys equipment (and swimmers?). As @ajw22 points out (thanks Allen) this area TA - Further Reading provides a very complete chemical explanation. But even that detailed analysis seems to lack that caveat or warning that you may still want to run at the low end under certain conditions. I don't think my conditions are all that unusual, just a 16K IG aggregate with spillover spa and SWG.

In other words, without the caveat how else is one to know that they could save a lot of time and money by running below this "ideal range"? Thanks everyone!

 

[ajw22]

As @ajw22 points out (thanks Allen) this area TA - Further Reading provides a very complete chemical explanation. But even that detailed analysis seems to lack that caveat or warning that you may still want to run at the low end under certain conditions. I don't think my conditions are all that unusual, just a 16K IG aggregate with spillover spa and SWG.

In other words, without the caveat how else is one to know that they could save a lot of time and money by running below this "ideal range"? Thanks everyone!

I think the discussion in the TA Wiki describes when running a lower TA is fine. TFP's goal is education, and the Wiki tries to help you decide on the best TA for your pool.

The Wiki says...

However, if a pool experiences constant acid demand and the pH rises too quickly, TA can be safely lowered as far as 50 PPM to compensate for this. Despite what the “pool experts” will say, keeping your TA on the low end will not “rot out your equipment” or “destroy your plaster surfaces.”

and...

Running a TA below 50​

The TA can be very low, with a pH in the 7 to 8 range. For example, if you have distilled water, you can have a pH of 7 with no bicarbonate or carbonate alkalinity. The only alkalinity you will have is enough hydroxide to make the pH 7 vs. 4.5.

At a pH of 7.0, the TA from hydroxide is 0.0000001 moles per liter or about 40 grams in 10,000,000 liters, which is about 0.005 ppm TA.

If you keep the TA very low, calculate the carbonate alkalinity by subtracting the cyanurate and borate alkalinity.

You can use PoolMath to monitor CSI and keep it in a good range. Get PoolMath and keep the CSI in the -0.3 range for the heater and the fiberglass warranty, even though fiberglass and copper should not need CSI.

Low pH puts heaters at risk, so you must be extra careful not to allow the pH to crash, even briefly.

You can go lower than 50, but it requires special attention to several issues that can become problems.

You have less buffer, so you get more movement from added acid. You have to be extra careful not to add too much acid and drop the pH below 7.2.

 

[Saturn94]

Are you sure it’s the salt?

It’s either the salt, city water, or combination of both.

 

[nuttyp]

think the discussion in the TA Wiki describes when running a lower TA is fine.

You're right, I stand corrected, thanks Allen, the caveat is in there, at least for those who dig into it. "However, if a pool experiences constant acid demand and the pH rises too quickly, TA can be safely lowered as far as 50 PPM..."

 

[Bperry]

Pool math: 60-80 "ideal"
Google ai: 80-120 (most pool stores recommendation)

I think the confusion is "ideal", which depends a great deal on all other variables. Shoot for CSI of -.25? Curious what the "ideal" numbers are for those who didn't need to clean calcium from their cell.

FWIW, update to the latest poolmath app and the “ideal” problem goes away. There’s just a straight recommendation of 50-90 now.

 

[generessler]

Re the iron, thanks for the testing effort and putting the info up. I do wonder how valid it is to infer that all salt of a given brand has certain iron (or anything else) content from a single or small number of samples. For example, we've had threads here reporting disasters with Morton, which in this thread is favored. In my case, Solar Crystals - which prior to this had no negative reports - raked out across the shallow end are gone in less than 20 minutes even if the water is cold. Never anything like a stain. Big shrug...

 

[AUSpool]

This thread seams to have a bit of a split personality.

Salt.
That AquaSalt looks pretty good statistically. 99% NaCl. (Typical Analysis, 99.9%). It would be nice to know what the stain blocking additive is but given its food grade is probably nothing sinister. They are kind of none specific about production methods. There is a reference to two new plants and one at Saltville, VA. Looking at Saltville, VA on google earth there doesn’t seem to be a lot in the way of open evaporation ponds in the area.

The percentage purity interests me. We have a bit of an obsession with mineral or magnesium salts here in Aussie. The percentage purity of that stuff is only 95-98%, at 98% thats just under 2 cups of impurities per standard bag (40lbs).
The stuff I use is 99.4% which has about 24 tea spoons of impurities.
At 99.8% there would be 8 tea spoons of impurities.
When sea water is used for the input stream the vast majority of the impurities will be magnesium, calcium and sulfate.

Alkalinity.
I haven’t been in a pool shop for testing and the recommended adjustment for years. But I cant help but wonder what the conversion would be.
Pool shop: Your TA is 80 which is too low.
Me: Why, the range is 60 - 120 isn’t it?
Pool shop: You need to add “TA up” to bring it up to 120.
Me: Why, do you have an ideal target within the ideal range.
Pool shop: Well no, we just like to bring it up to 120.
Me: So your ideal target is 120, don’t you think its a bit odd that your ideal target is at the top of the ideal range.
Pool shop: Hah. And at 7.8 your pH is too high, you’ll need to add some acid.
Me: But wont that decrease my alkalinity.
Pool shop: Not if your just adding a little bit.
Me: So it will just decrease my alkalinity a little bit, a little bit every time I add it.
Pool shop: Hah?

Or maybe not.

But I cant help to think that there are a couple of things to remember. Our town water supplies all have carbonate alkalinity at some level. While carbonate alkalinity is good at resisting an addition of acid or a decrease of pH it’s not that good at resisting an increase in pH. Increasing the carbonate alkalinity will increase the concentration of dissolved CO2 which will force the pH to rise.

pH and TA management will be different for each pool but I believe the simple approach is to manage your pH and let your TA settle where it wants to be without totally ignoring it of cause.

FWIW, an old Limnology book I have talked about alkalinity in several places but doesn’t actually but a figure on the alkalinity of lakes and rivers. If you dig a bit it is sometimes given at around 20ppm but the natural system is dynamic with a lot as acidic processes that both consume carbonate alkalinity an produce it in a kind of ballanced state. But that cant be directly compared to supply systems or a back yard pool.

 

[nuttyp]

FWIW, update to the latest poolmath app and the “ideal” problem goes away. There’s just a straight recommendation of 50-90 now.

Indeed I think that is worth the effort, I think it may help folks & thanks for pressing forward the change. The 50-90 range is evident when one clicks on TA from the Overview area (in the app). That said, the other sources remain for folks to watch out for, such as:

** ABC's landing page says "50 to 90ppm, sometimes higher" with no real warning except that it says "High levels can cause pH to rise" (from here: https://www.troublefreepool.com/blog/2018/12/12/abcs-of-pool-water-chemistry/_​

** Recommended values from web landing pages (linked also by the app when clicking recommended levels) show the same banner I posted earlier, re-pasted below, produced when you plug in plaster and swg to that tool - from here: What Are My Ideal Pool Levels? I suppose one could construe that to still mean 50-90, but....​

** Another data point: In the app under "chemical additions" if I tell it I'm going to add 5,10, or15 lbs of baking soda to my 16,000 gallon pool, under estimated effects in says it will raise PH by only 0.1. Is that possibly correct - or possibly misleading?​

​

Being an electronics engineer and not a chemist, I only know that any time I try to press my TA towards 80, I get PH rise every week thereafter by at least .3, thus I wind up adding muriatic acid at about 16 ounces per week until the TA settles back toward 50 or 60, then the cycle starts again. So I still think one of these versions of a caveat might help folks if it were found anyplace we discuss TA:​

A) "If a pool experiences constant acid demand (i.e. constant PH rise) TA can be safely lowered as far as 50 PPM... OR​

B) "If a pool experiences constant acid demand (i.e. constant PH rise), Read here: TA - Further Reading​

​

But that's just me and my pool. I know it happens to others, but I don't really know how common the problem truly is.​

​

This thread seams to have a bit of a split personality.

Yes, split personality It all started early when @Bperry astutely (and thankfully) noticed that me and at least a couple other members were having to regularly clean our SWG cell of calcium and the cyle we're in, of adding TA and MA all the time. Still thinking about splitting off a new thread about the TA debate, just that I'm still not a chemist and unsure just how common the problem is.

I haven’t been in a pool shop for testing and the recommended adjustment for years. But I cant help but wonder what the conversion would be.
Pool shop: Your TA is 80 which is too low. ...etc

Good insight, I'm guessing that conversation happens very often - maybe hourly! I feel like it happened in my head, right here in TFP, because I read the recommended levels without digging deep enough to discover that a TA of 50 may be far better for me, or just letting it float down until PH stabilizes. I like what you wrote in summary below:

pH and TA management will be different for each pool but I believe the simple approach is to manage your pH and let your TA settle where it wants to be without totally ignoring it of cause.

 

[nuttyp]

do wonder how valid it is to infer that all salt of a given brand has certain iron (or anything else) content from a single or small number of samples.

I agree @generessler. I did note that in the OP, that the iron content may vary from batch to batch, but I think it was worth your underscore!

 

[Bperry]

** Another data point: In the app under "chemical additions" if I tell it I'm going to add 5,10, or15 lbs of baking soda to my 16,000 gallon pool, under estimated effects in says it will raise PH by only 0.1. Is that possibly correct - or possibly misleading?​

Baking soda raises the pH very little to none so it’s not misleading. The resulting TA increase from baking soda can lead to faster pH rise but the baking soda is not the direct cause and not the only cause.

Note that a TA of 90+ is a good idea if you are using trichlor for chlorine because the trichlor will tends to push your pH (and TA) lower which can make the pH get unstable when TA gets too low.. but that’s a longer term reaction and not an instantaneous direct result.

 

[JamesW]

If a strong magnet sticks to the side of the bag of salt, then that is a bad sign.

 

[ajw22]

If a strong magnet sticks to the side of the bag of salt, then that is a bad sign.

If a weak magnet sticks to the side of the bag of salt, then that is a worse sign.

 

[AUSpool]

I agree @generessler. I did note that in the OP, that the iron content may vary from batch to batch, but I think it was worth your underscore!

There will likely be differences between batches and the occasional bad bag due to contamination.

I think most of the brands have multiple plants and extraction methods. It may be helpful to go back to the original analysis and check each products % of purity and if they provide it, a list of common impurities. There is likely a direct link between purity and iron content. Iron content would also be linked to where the salt is mined or collected from, or the source water used for extraction via crystallization.

For most of us the best selection criteria would be the percentage of purity where the highest is obviously better.

 

[nuttyp]

Baking soda raises the pH very little to none so it’s not misleading. The resulting TA increase from baking soda can lead to faster pH rise but the baking soda is not the direct cause and not the only cause.

I get it, at least from a purist sorta perspective, so thanks. I'm just not sure how much it matters to me that the relationship is direct or indirect, since I'm reliably having that experience - and presumably the reason you and others advised me and @tcat to lower TA and thereby exit that cycle. I'll know for sure after some weeks/months of keeping the TA lower.

Early on I also mentioned my spa spillover/waterfall (also in my signature), about 20 GPM 11 hrs/day, and that aeration is surely contributing to the PH rise. But there is one other data point....

If I plug in some standard "neutral or recommended" values into the original online poolmath and then add 7 lbs of baking soda to raise the TA 30 ppm, the tool predicts a substantial rise in CSI by +0.26. Granted that's CSI, not PH, influenced by other things (CA & CYA among them), it is still the case that the tool is telling me CSI will rise by by .26 by only adding 30 PPM of TA. The "fix" would always be to check PH, find that it rose (indirectly I guess) then add acid and bring down the PH, thus lowering CSI as well. The cycle, as it were. Perhaps the "app" should at least include the CSI rise as an "estimated effect"? Full values pasted below from that little web tool experiment.

 

[Bperry]

I get it, at least from a purist sorta perspective, so thanks. I'm just not sure how much it matters to me that the relationship is direct or indirect, since I'm reliably having that experience - and presumably the reason you and others advised me and @tcat to lower TA and thereby exit that cycle. I'll know for sure after some weeks/months of keeping the TA lower.

Early on I also mentioned my spa spillover/waterfall (also in my signature), about 20 GPM 11 hrs/day, and that aeration is surely contributing to the PH rise. But there is one other data point....

If I plug in some standard "neutral or recommended" values into the original online poolmath and then add 7 lbs of baking soda to raise the TA 30 ppm, the tool predicts a substantial rise in CSI by +0.26. Granted that's CSI, not PH, influenced by other things (CA & CYA among them), it is still the case that the tool is telling me CSI will rise by by .26 by only adding 30 PPM of TA. The "fix" would always be to check PH, find that it rose (indirectly I guess) then add acid and bring down the PH, thus lowering CSI as well. The cycle, as it were. Perhaps the "app" should at least include the CSI rise as an "estimated effect"? Full values pasted below from that little web tool experiment.

View attachment 622550

I use the phone app so maybe different. If you open the CSI tab it’ll show the effect of changing any individual other parameter including TA. That’s what I use when estimating changes.