Iron from Salt

[tlhwxman]

Hello all,

Still continuing to work my iron staining problem. I have some interesting results from the iron testing that I am doing. I want to run some things by the group to get their experiences.

I have been trying to track down the source of the iron getting into my pool. So, I have been testing sources. I tested the city water (negative), the rain water (negative). I then decided on a whim to test the salt I use for my SWG. I use the standard Morton's Pool Salt.

When I tested the pool salt (dissolved in a solution) it read 0.30 ppm Iron. I know you can get iron from salt, but I always figured that Pool Salt would be free of iron. Surprising result to be sure.

What has been your experience with salt and iron content therein? What salt can I buy where the iron content is assured to be minimum or none??

Thanks
Todd

 

[Suziqzer]

I've never bought "pool salt", just simply solar salt in the blue bags and never had any staining issues or problems so far in 3 years.

 

[Swampwoman]

Todd, did you dissolve it to represent the ratio to which it's in your pool -- eg. recreating 3200 ppm?

Interesting results nonetheless. I don't add salt, and I do have well iron, so it's no mystery to me where mine is coming from
BTW, in the interest of mystery iron, were you aware that fertilizer blow-in can add iron?

 

[RobbieH]

Why do you think you can get iron from any salt?

 

[Swampwoman]

^A teaspoon of regular table salt has about 20-25 ppm of iron in it, from what I recall. That's likely the known fact to which he's referring. (Some types, like himilayan, have closer to 40 ppm).

However, if the salt to water ratio is about 3000 ppm, then it's not likely the regular known iron in salt would actually be .3 ppm when diluted in the pool water, unless my math is rusty (which it is, so forgive me if I'm "all wet" here

 

[RobbieH]

Great puns!

 

[JasonLion]

Morton solar salt has about 0.3 ppm of iron in the salt. Once diluted to 3000 ppm of salt in the pool that comes out to roughly 0.001 ppm of iron added to the pool by the salt. That isn't enough to even show up on the test.

Other brands/kinds of salt have different levels of iron, some up to 100 times as high. But even that would only be 0.1 ppm of iron added to the pool from adding salt.

 

[tlhwxman]

Darn it! The ratio (salt/water) was not consistent with that in the pool. It was much higher So, based on your responses the salt may not be the culprit. If diluted it would not rise to the level being a problem. Ugh! Back to square 1.

I have done a 75-80% water dump on the pool and the iron came back. That tells me it is coming from somewhere. Tested the input water, tested the rain. The pool store and the pool company both say this is not a common problem in the local area at all. All piping is PVC (installed in 2007). No heater is attached. Something has to be adding iron

One questions that just popped into my head. If the iron is suspended in the pool, does it evenly distribute through the water? In other words, will it pool at the bottom? If so, perhaps the water swap would not work since the 20-25% I left in the pool was riddled with iron. Just a theory.

Todd

 

[JasonLion]

The test is measuring dissolved iron, which is uniformly distributed throughout the water. However, it is possible that the dissolved iron is coming from small iron grains that have accumulated somewhere and are slowly dissolving.

 

[tlhwxman]

Jason - thanks for the reply that helps. FYI - I ran a test with the proper ratio of salt in a gallon jug. It registered between 0.0 and 0.15.

What is really strange is that I cannot sequester this iron. I have had Jack's Purple up to 16ppm (w/6.8 pH and low FC). It still required a 32 oz bottle of Jack's 5 days to one week. The folks at Jack's suggested that something is breaking the bond once the iron is sequestered (thus using up sequestrant rapidly). That is why I have moved away from that solution. At that rate, buying jack's Purple would cost a bloody fortune.

That is why I am trying to track down the iron source. I may be able to lick the problem that way

Todd

 

[Swampwoman]

Have you looked into electrical bonding issues at all?
I've read a few threads now that reference small amounts of current possibly having a corrosive impact... Just a thought. I haven't read your other threads so I don't know your history of iron staining.

I have well issues but am using softened water now plus pre-filtering AND sequestering (yes, Jack's gets expensive) yet still get faint staining...So I'm reading everything I can get my hands on

 

[Richard320]

I've never met a successful alchemist before! Can you make gold or platinum out of salt, too?

:joker:

I found my source of iron when I opened the strainer on my spa booster pump. Someone had left a inflatable pipe plug with its chain in there. It was just a blob of rust, that chain was never going to unwind again.

 

[tlhwxman]

I found my source of iron when I opened the strainer on my spa booster pump. Someone had left a inflatable pipe plug with its chain in there. It was just a blob of rust, that chain was never going to unwind again.

Funny you say that Richard. That thought cross my mind. Did someone leave a surprise during my install years ago? It's possible that some piece of metal is caught up in a valve or the filer or piping. Hmmm.