It may be possible to greatly reduce iron in pool water

chem geek

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Baquacil Oxidizer (NOT CDX) at $13 per gallons is 27% hydrogen peroxide and the best value for it at 48 cents per % while the Walmart 7% is 57 cents per %. Not a huge difference though.

I would not use hydrofluoric acid since it's too dangerous and we don't know how badly it may etch a plaster surface. Muriatic Acid is already harsh enough. If hdjii wants to try your hydrogen peroxide and ascorbic acid method followed by the Jack's Magic Purple Stuff (HEDP and PAC copolymer) or Magenta Stuff (PAC copolymer), that's up to him. When you add back the chlorine, the hydrogen peroxide and ascorbic acid will go away (well, the ascorbic acid will get oxidized to dehydroascobic acid). The Jack's Magic HEDP is something we'd recommend for metal staining anyway and the PAC copolymer should get mostly filtered out at some point depending on what else is in the water (i.e. if flocculation occurs).

If your method doesn't work for him, then a drain to do a manual acid wash will remove everything in the water anyway. The only harm done would be the expenditure if the method didn't work. Just keep in mind that you are the only one who has done this method so we don't have decent stats on how effective it will be in general.
 

smallpooldad

Well-known member
Aug 6, 2008
429
Honolulu
Chemgeek,

Thank you for the advice.

And

hdjii,

Below is the Method I would now use if I were to repeat it. I did not cover phosphate testing but it is a good idea to do before the method and interesting after the second Phosfree removal at the end. Nor did I cover TDS but I will insert that later, as a TDS reading is only really needed at the end, and for interests sake at the beginning.

THE HP WITH AA METHOD
(Completely Revised as of 2-22-2014)


THIS IS EXPERIMENTAL AND NOT INEXPENSIVE.

But it worked for me and is not aggressive.


Please remember this may take 1, 2, or 3 treatments before all is done. It will not get rid of underlying organic stains (organic staining underneath scale) for this you will have to wait 4 to preferably 6 weeks to shock your pool for 1 to as long as 5 to 7 days if they are bad. Personally I use the mustard level shocking levels as my starting point as it seems to do a better job, and is not that much higher than the regular shock levels. It will make a noticeable improvement to an old pool that has been neglected, or had large amounts of scale.

All calculations are for a 10,000 gallon pool of plaster construction, it has not been tested in any other type of pool.

1. The colder the better, anything under 77F should work, under 70F will be much better. If you pool heater, or solar panel, has a copper coil it must be isolated from the pool water with bypass valves, titanium are fine.

2. You will need one bottle of "Jack's Magic Purple Stuff" per 10,000 gal. I do not know the quantity for "Metal Magic".

3. You will need Ascorbic Acid (AA) (1 1/2 lb per treatment/2 lb for heavily stained pools) for better results make sure the pH is set at 7.2 - 7.3 before adding the AA.

4. You will need the following amounts 3% Hydrogen Peroxide. The amount is 1152 ozs for each 10,000 gallons, plus a pre-treatment amount to remove chlorine ppm to zero at 21 oz HP per 1 ppm of chlorine. If you are using 27% HP then divide these number by 9. Pour this around the pool, not through the skimmer. Preferably allow your pool cleaner to mix it. 27% is available from Hydroponic Stores, or some Garden Nursery Stores, it saves time opening 40 plus bottles of 3% HP. Or the Baquacil Oxidizer, chemgeek refers to above.

Why so much HP: The amount of HP is far higher than I originally used, but is far more effective; as I discovered, by experimentation, a swimming pool is not a sanitized boiler.

Note 1: Do not use Thiotrine to lower your chlorine levels the HP does that and also acts as a sanitizer, albeit not as good as chlorine.

Note 2. The higher the Hydrogen Peroxide % the faster it loses its effectiveness over time, so check the "good by date" or "expiration date" do not use old bottles, or ones that have been sitting in the store collecting dust.

5. Do not use Algaecide 60, make sure you Free Chlorine is holding with less than 0.5 difference, before effecting the treatment. Well you could use Algaecide 60 but I think it might interfere with the HP and you will need more chlorine later to get your pool back to the right level of Free Chlorine.

6. First put the filter on bypass.

(Very Important) First add the HP in darkness, sunlight destroys it, even light from a room and moonlight can more quickly reduce it strength. Allow it to mix in your pool for two hours (it takes that 2 hours before it will start to work in the water) before adding Ascorbic Acid. Remove pool cleaner before adding Ascorbic Acid. Add Ascorbic Acid (AA) After 2 hours at a rate of 1 1/2 lb minimum (for heavily stained pools 2 lbs would be good) for 10,000 gals. Again make sure you removed pool cleaner before adding Ascorbic Acid, and have bypassed your heater if necessary.

7. The HP only is effective for up to 7 hours after that it stops doing it's job so (Very Important) before sunrise add 931 oz of Walmart's Plain Extra Strength Bleach (8.25% Chlorine), this is equal to to 7.7 "121 oz jugs" to get your chlorine levels up to about 10 ppm. Then check your chlorine levels after 4 hours to adjust, if too high they will go down. This amount is very important as it will avoid low chlorine, which is sometimes an issue with the AA method.

And immediately add 110 oz of Muriatic Acid to control the pH to a level of 7.2, and avoid it riding above that.

8. NEVER EVER NEVER continue the treatment into the next day after Sunrise as Hydrogen Peroxide is destroyed by sunlight and you do not want to get an algae bloom.

9. Turn the pool filter back to filter. Than check the pH and Chlorine levels, and adjust the pH to 7.2 - 7.3, and the Chlorine to around 9 or 10 ppm, this should be checked every 2 hours, for the first 6 hours. After the first 2 hours vacuum the pool, and then back wash you may need to repeat this process over 3 times in a matter of 8 hours.

10. If you live in say West Texas, Central Valley CA, parts of Florida and have really, really bad scaling issues you may be looking at 2, 3, or possibly 4 repeat treatments, but I would still prefer this over an acid wash any day as this is far less damaging to the pool finish. And yes I have had an acid wash, and never ever again will I do that.

11. Once ALL 1, 2, 3, or 4 of your treatments are done, and backwashes, keep your pH at around 7.2 or 7.3, then pour 52 oz of the very expensive "PHOSfree Commercial Strength", manufactured by "Natural Chemistry" into the skimmer after very, very, very strongly shaking it (it is a poor mixer). Do not use the regular stuff as it is not Aluminium based and will not remove scale or iron, only phosphates, we are after removing iron and scale from the water. The pool will become very cloudy for 1 to 2 days. Run the pump and cleaner for 48 hours, then backwash.

Repeat one more time, adding 52 oz of "PHOSfree Commercial Strength". The pool will become less cloudy for 1 to 2 days. Run the pump and cleaner for 48 hours, then backwash. This should have removed most of your scale in the water and iron, manganese, phosphates and other contaminates. Once every month add 4 oz of PHOSfree Commercial Strength to your skimmer, more often if you have heavy duty iron in your fill water.

12. Then add one bottle of "Jack's Magic Magenta Stuff", and 4 -5 oz a week for normal iron and scale control, more if necessary. Set the pH at 7.5, and re-balance.

Note: I stopped using Jack's Purple Stuff and use the Magenta, with more success. I ran the pool at a pH of 7.7, but went back to 7.5 for sanitation reasons, with no staining issues at the higher pH whatsoever for about 2 to 3 months. The "Magenta" is a Copolymer and so binds up scale and metals for removal to the filter. The Purple stuff, keeps then in solution at a pH below 7.4 in the pool, but does not trap them in the filter for removal. However please note water treatment plants use both chemicals, so one can use both if that works better for you. This might be especially true if you are in an area where the fill water is heavily contaminated with iron, then a pH of 7.4 or 7.3 might be appropriate. If scale is more the issue then 7.5 or 7.6 might be OK.

My personal experience is that the Magenta stuff continued to remove scale from the walls over a period of many months (plus 4), you might also notice your calcium levels increasing as this de-scaling is going on. The calcium levels will eventually stop increasing, I think that is because most of scale has been removed. I also have/had a small manganese stain from construction, about the size of a half dollar, that is slowly but surely being removed. Just a few match stick size heads are remaining.

13. Wait 4 days after treatment to check your CyA reading as it may give you a false low reading, by this I mean 80 ppm may only read 50 ppm for a few days, and 50 will be 30, although you actually have 80 ppm or 50 ppm, of which 30 ppm, or 20 ppm, went dormant but will return.

Warning: Never add water to acid only acid to water

My experience is that if you have heavy scaling over a number of years, above 6, 2 if you live in Texas or California's Central Valley, and if you have been using an HEDP sequestrant for a long time you probably have fairly high orthophosphate levels, over 7000 ppm, so the first treatment will work primarily on getting these levels down with some effect on the of iron, manganese, scale, and copper stains. The use of ascorbic acid will help a lot in the removal of metal stains more so than just HP alone, these will then either oxidize or be removed by the filter backwash.

The second treatment, if necessary, will do the same again but this time it will work more on the scaling issues, and the third treatment (if necessary) should have gotten rid of most if not all the calcium, calcium phosphate, or iron phosphate scaling. And it seems to me that the iron is gone and I do mean gone I do not think it is even in solution in the sequestrant, or if present there is very little there.

If you have not been using an HEDP sequestrant for a long time then maybe 1 or 2 treatments might work.

hdjii,

I will post some minor recommendations over the next few days in this post via editing, on phosphates and TDS, but the above is really all you need.

Hope this helps, and good luck if you do it.

Please, please let us know if it worked for you. As you can see from some posts on this subject this method is viewed in the same light as heliocentrism was in the early 17th century, you may or may not be able to dispel this theory. Fortunately we live in the 21st century and I cannot be burned at the stake, just anonymously humiliated on the net. And then I will have to "abjure, curse and detest" my opinions. However I am a great believer in Einstein's words, "The only thing that interferes with my learning is my education."
 

hdjii

Member
Aug 16, 2012
6
smallpooldad:
Thanks again for your input.

From the 2012 Manatee Co. Water Quality Report:
"Drinking water for the customers of Manatee County Utilities Department is a blend of purified
groundwater and purified surface water. In 2012, an average of 13.66 million gallons per day of deep
ground water and 24.71 million gallons per day of surface water was used.
The groundwater is pumped from the Floridan Aquifer from seven, 1200-foot deep wells located
in eastern Manatee County. This water is pumped through a 36-inch pipe approximately 13 miles to
the Purification Plant. Surface water is taken from the Lake Manatee Reservoir located in central
Manatee County."


Further, in an addendum to the Water Quality Report, the average 2012 concentrations of many of the parameters of interest are shown.
First, in parts per million: Sulfate 93, alkalinity (as CaCO3) 33, TDS 228, and total hardness (as CaCO3) 133.
Second, in parts per billion: Al 71, Mg 20, Fe 32 and Zinc 148.

I will also have the tap water tested by my local pool store for TDS and see how it compares with the County data.

The toilets in my home did indeed shows reddish brown deposits in the water tanks when I moved in. These deposits were easily removed with Super Iron Out which contains sodium hydrosulfite and bisulfite according to the label. This is a consumer product. After about 18 months, light reddish deposits have reappeared.

I will obtain a phosphate test kit and report the results. If I can't find this locally, I will order it online which will take a week or so. In any event, I will have to order the Jack's Magenta Stuff as it is not available on the shelf locally.

Draining the pool is the ultimate last resort and I would have that done by a professional in connection with a resurfacing of the pool. I do not want to do that.

Three questions:

1. The tap water pH is 7.4 on average. The range is 6.9 to 7.7 per the County.

2. I have kept the alkalinity and pH low in the hope that this would reduce the scale or at least slow or stop additional accumulation.

3. The alkalinity of the tap water is alkalinity is 33 ppm (as CaCO3) as reported by the County.

I have some work to do to get ready for this approach to removing the remaining scale so itwill take a while. Also, depending on the total time, cost and complexity, I may just do another in-situ acid wash since that did remove a lot of the scale when I did it.

Thanks again for your thoughtful input.

Howard
 

hdjii

Member
Aug 16, 2012
6
chemgeek:

Thanks for the tip on the source for hydrogen peroxide. Also, I appreciate the cautions you have provided. As a PhD inorganic chemist, I am comfortable with the handling of hazardous chemicals when it seems appropriate to me. For example, I use HF sometimes for spot removal of rust stains, but it is too hazardous to experiment with on a large scale.

The progress I have made to date on this stain/scale problem is principally due to the advice and practical experiences reported on this forum by you and other pool owners. The ascorbic acid treatment for iron removal seems to be well established, low risk, relatively inexpensive and dependable. It certainly worked for me.

The in-situ acid wash has not been as widely reported and probably has significant risk to pool equipment, but the experience reported by TXFlyGuy and the details he provided, I felt that it was worth the effort and risk for me. As I said in my response to smallpooldad above, I may do another to see if it may be sufficient to remove the remaining scale. It did take more than one treatment for him.

Howard
 

Patrick_B

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Jun 7, 2011
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Just curious Howard, how do you apply the HF to remove stains? Interesting you are using it at all. I'm no Chemist, but I know a little about it as it pertains to refining Gasoline. And enough to know what it can do.
 

chem geek

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As a PhD inorganic chemist, I am comfortable with the handling of hazardous chemicals when it seems appropriate to me.
Howard,

Just FYI. In spite of my moniker "chem geek", I'm not a chemist (just interested in it and schooled in it but with no PhD), so you're ahead of me there. As you can tell from reading this forum, we try and look at scientific peer-reviewed sources whenever possible, but then validate any techniques through experimentation and observation.

Richard
 

hdjii

Member
Aug 16, 2012
6
Brushpup

Whink is an aqueous solution of HF which is 1.5 to 3.5% concentration per the MSDS. I have used it for many years to remove rust from clothing, tile, aluminum, sinks, tubs, etc. It is very effective.

The fluoride ion has a very strong affinity for iron, but HF is a very weak acid so I would expect its effect on pool surfaces to be minor compared to HCL which is a very strong acid. This is, of course, pure speculation since I have not actually tried it on my pool surface. It would be expensive in large quantities I expect and I would not want to handle large quantities of it anyway.

Howard
 

hdjii

Member
Aug 16, 2012
6
chem geek

Although my education is a great help in understanding the terminology and following the discussions in this forum, the solutions to the problems encountered in caring for a pool only emerge from the intelligent analysis of the actual practical experiences of those who maintain pools. This is where you and others on this forum excel.

As an alternative to the self serving advice provided by most pool stores, this forum is invaluable. It has helped me cut through the clutter of misinformation to gain a clear understanding of how to care for a pool with effective and economical methods. I am grateful to you and all who participate in the forum for the time you invest.

Howard
 

chem geek

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Thanks for the compliments.

Yeah, I noticed the pKa of HF being only 3.17 so my concern wasn't so much the acidity as whether fluoride ion attacks plaster. We already know that sulfates can have a negative effect so I was just concerned about a new ion for which we don't understand the possible chemistry. A conservative concern not based on any science that we know of. This presentation talks about HF hazards including attack on concrete, but that may just be from it's acidity when concentrated in which case HCl would be even worse. On the other hand, the fluoride ion's affinity for calcium could replace carbonate and possibly weaken the concrete structure (I'm speculating).
 

chem geek

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Mar 28, 2007
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Regarding the use of PHOSfree Commercial as a source of PAC, note that the latest MSDS for Natural Chemistry® PHOSfree Commercial Strength says it has

5-10% Lanthanum(iii) Chloride Heptahydrate
3-7% Aluminum, water-soluble salts, n.o.s.*** (I believe that "n.o.s.***" means "not otherwise specified")
3-7% Zinc chloride

So it still contains aluminum for an alum floc, most likely to be able to clear the water of the lanthanum carbonate that would form and make the water cloudy. Though an alum floc will also remove silica, polyaluminum chloride (PAC) is apparently better as described in this paper along with polyacrylic acid (PAA). So once phosphates are removed, you might be better off getting PAC directly as it should be less expensive than the PHOSfree product since lanthanum is expensive.
 

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smallpooldad

Well-known member
Aug 6, 2008
429
Honolulu
hdjii and chem geek,

A few questions and then some observations, and finally a few more questions.

Questions:

It is sad to note that Natural Chemistry changed the formula for "PHOSfree Commercial Strength", it seems they also are changing the name to "PhosFree Extra Strength", as I doubt any commercial water treatment facility might use it. Regardless of this and its high cost it seems it might still remove silica, which is a concern to me, but would it also continue to remove iron and manganese? If not I will write a caveat to the above instructions.

What purpose does Zinc Chloride serve?

Where might one be able to purchase Polyaluminum Chloride (PAC) as a replacement, in small quantities, and how should it be mixed? The minimum quantity I can find is a 95 gallon drum.

Observations and Questions:

hdjii, you wrote that you will forgo at present the HP and AA method, in favor of another in-situ water acid wash to see if that finally solves your issues, as you did remove a lot of material the first time. That seems like a good idea to me, hopefully it will resolve your scaling issue if all, or most, of it is calcium carbonate scale. If however it is calcium silicate scale, the type of scale I was dealing with, then it might not be so successful. See here::

http://www.lesliespool.com/blog/pool-care/pool-chemicals/dealing-with-scaling-and-staining/

http://www.mcgrayel.com/files/cleaning_tips.pdf

However I will add your excellent point as a caveat to the above instructions, as some persons have little or no calcium silicate scale. The HP and AA method might not then not be a persons preferred treatment as it is more costly, although less acidic. They would then have 3 options, this would include the drain and acid wash as well.

The only small concerns I have regarding the in-situ water acid wash are that if the pump seal were a not too new the acid might leak into the motor/housing. If a small pin prick leak existed, checking underneath the pump to see if there is not a wet spot might be a good idea. That, needless to say, should be fixed with a new seal immediately, as the pump will eventually break anyway. And what would be the effect on a copper coiled heater, a SWG cell, or monitoring tip as used in the PoolPilot automated set-up, that cannot be isolated for the period of days that this low pH treatment needs to be done? And finally an old pool with old plaster?

As regards an HF method I think one would be crazy to attempt it as it might kill a person(s), and quite possibly seriously damage the plaster. Very experienced, and expensive professional companies might be able to do this successfully.

If you are successful with the in-situ water acid wash, I still believe a weekly dose of an Acrylic Acid Copolymer, such as Jack's Magic Magenta Stuff, would still be a good idea to control both metals and silica. This is based on personal experience of having no re-staining of iron after nearly 6 months. Then you may not need to fight the pH down to 7.4, but keep it in the 7.5 to 7.7 area.

Lastly based on the very small number given to you by your water authority for iron in ppb, it seems odd the toilets had red stains. We have very low iron in our municipal water and see no red stains in the toilets, and we are literally at the end of the line, very near the top of a mountain. Or it could be that we are lucky in that all the homes on the way up are getting the iron before us. Are you sure it is in ppb and not ppm?

Your thoughts are welcome.
 

chem geek

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What purpose does Zinc Chloride serve?

Where might one be able to purchase Polyaluminum Chloride (PAC) as a replacement, in small quantities, and how should it be mixed? The minimum quantity I can find is a 95 gallon drum.
I don't know the purpose of the zinc chloride. As for purchasing PAC, unfortunately I couldn't find any standard pool brand that has it. It is very commonly used and available in the commercial pool market but as you point out it's sold in rather large quantities in that situation. It's particularly used in Europe since DIN 19643 requires flocculation using either iron or aluminum.
 

chem geek

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Unfortunately that link and others I've looked at don't help with regard to figuring out why they added zinc chloride to their PHOSfree Commercial. The lanthanum is clearly used to precipitate lanthanum phosphate and the aluminum salts are clearly used for flocculation/coagulation to help clear the water of the lanthanum carbonate that forms, but the zinc chloride is a bit of a mystery.
 

JamesW

TFP Expert
Mar 2, 2011
24,192
Not to get off topic, but I would like to emphasize just how dangerous Hydrofluoric Acid is. I think that it should be made clear that it would not have any use in a pool or in any type of pool service. See this reference:

http://web.princeton.edu/sites/ehs/labsafetymanual/cheminfo/HFFactSheet.pdf

Also from the reference chemgeek posted:
Hydrofluoric Acid is one of the most dangerous acids known. It needs to be treated differently than even strong acids like Sulfuric and Hydrochloric.
Hydrofluoric Acid is an acid like no other. It is so potent that contact with it may not even be noticed until long after serious damage has been done. Even very strong acids, and mixtures of acids, like Aqua Forte and Aqua Regia, do not have the power to cause death and injury in the way that Hydrofluoric Acid can.
http://web.utk.edu/~ehss/training/has.pdf
 

JamesW

TFP Expert
Mar 2, 2011
24,192
Smallpooldad, I don't understand how the hydrogen peroxide works to remove iron. I know that it can reduce iron, but it's just as likely to oxidize it. Can you explain how it works?

Also, wouldn't the ascorbic acid and the hydrogen peroxide just neutralize each other?
 

chem geek

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See this thread where I speculated about using hydrogen peroxide where some comments indicate that it might work. Yes, it is both a reducing agent and an oxidizer, but perhaps as a reducing agent it lifts stains while as an oxidizer it precipitates rather than stains. That is, it may just accelerate the transfer process from insoluble to soluble and for whatever reason becoming insoluble again occurs as precipitate in the water that presumably can get filtered out. Note that the treatment seems to work best at low pH (closer to 7.0) and that may be why the iron tends to oxidize in the water rather than re-stain since higher pH tends to cause more staining for whatever reason.

Then see this thread. In that thread in this post I refer to a paper that talks about how iron can precipitate phosphate and that hydrogen peroxide can aid in that process. So if one has phosphates in the pool, say due to a lot of use of HEDP, then one can presumably remove the iron by precipitating it with phosphate aided by hydrogen peroxide. As to whether phosphates are required for this use of hydrogen peroxide in removing iron stains to be effective is an open question.

When using ascorbic acid, you would add that first to remove the iron stains and you would add the hydrogen peroxide later presumably to precipitate the iron so that it can get filtered out. And yes, I'd expect the two to react, but one can never be sure since reaction rates aren't the same as thermodynamic possibilities.
 

JamesW

TFP Expert
Mar 2, 2011
24,192
It will be interesting to see if anyone else gets the same results. However, I think that it's too early to suggest the method as anything but experimental.

Also, a note about the baquacil oxidizer. It is a stabilized hydrogen peroxide solution and does not break down quickly in sunlight.
 

smallpooldad

Well-known member
Aug 6, 2008
429
Honolulu
chem geek,

Thank you for answering JamesW's questions for me. You are far more capable and knowledgeable than I at explaining these processes, and it was a very clear answer.

The only thing I do different from your explanation is to add the HP 2 hours prior to the AA. I am not sure if that makes any difference in the reaction, although it has worked for me.

JamesW,

I agree it will be interesting to see if anyone else gets the same results. But my main purpose in using this method is to remove calcium silicate scale, which is stated by many sources to be far harder to remove than calcium carbonate scale. A number sources state extensive calcium silicate scale cannot easily be removed by Muriatic Acid although I do not know if that is really correct or not, and some that Muriatic Acid will not work.

The possible removal of iron (I have no way of measuring it, but it is mentioned in a number of technical papers, albeit I used far more HP than water treatment plants use as a percentage) and definite removal of phosphates (I measured about 70% with HP) is an added bonus. My main control method for iron re-staining is now the Acrylic Acid Copolymer, presently supplied by using Jack's Magic Magenta Stuff.

I do think that it did removal iron from observation. The reason I believe this, is that one-time after doing the treatment I accidently raised the chlorine to too high a level, using a 5% measure when I had 8% chlorine. It rose to around the 10 -12 ppm area, and there was no iron stain re-occurring.

The old formula Natural Chemistry "PHOSfree Commercial Strength", did remove iron as it contained Aluminum Chloride, and was my primary method to remove iron, immediately after the HP/AA treatment. I do not know if the present formula does it as well, as it is Alum based. Chem geek states it will still remove silica, and that is a concern for me on the island of Oahu, as our water does contain 55 -65 ppm silica, so I will use a little of the new formula (4 - 8 oz) each 3 months to control silica. The other islands of the Hawaiian chain get their water primarily from rivers and streams, we do not, so they for the most part do not suffer this issue.

chem geek,

How good approximately , if any, would the new formula Natural Chemistry product with Alum versus Aluminum Chloride be at removing iron and other metals, versus the old formula in percentage terms?

Would the baquacil oxidizer being a stabilized hydrogen peroxide solution, and not breaking down as quickly in sunlight, make any difference to the overall method, or results; bearing in mind the HP and AA method recommended above neutralizes the HP before sunrise with large chlorine additions?

A question in regards to Zinc Chloride, I have read that it is used in the galvanization of metals, iron being one of them. Could it be used to the protect the motor, or other metal parts present in the pool? This might be the case if Lanthanum(iii) Chloride Heptahydrate is in someway corrosive to metals. Or would it bind/galvanize, in the presence of HCL acid, with iron to make its removal easier?

JamesW,

The reason I wished to remove calcium silicate scale is analogous to the following. If you went outside and painted a board with white paint and it had not dried, and the wind was blowing, you might get bits of dust and dirt sticking to your board. The board would no longer be pure white as it was still sticky when the wind blew.

Calcium silicate scale is just like sticky paint but it never truly dries allowing iron, other metals, and dirt to become trapped/glued on it, and then staining your pool. You might with AA remove the surface dirt but it would fairly quickly attract more such particles thereby re-staining over a period of time, requiring another AA treatment. By removing the calcium silicate scale one has removed one of the main causes of iron staining. If one is also able to bind, remove, and control iron, etc. moving them to the filter, with a chemical, such as an Acrylic Acid Copolymer, to be later backwashed, hopefully one may never have to do remove the calcium silicate scale again, or at least infrequently.

This chemical also removes silica, preventing further calcium silicate scale build-up.

You probably already knew this, so please accept my apologies. But others may not understand the reason for removing the silica scale, that is the reason for the explanation.
 

JamesW

TFP Expert
Mar 2, 2011
24,192
I'm not sure what you're using to dissolve the silicate scale? Is it the hydrogen peroxide?
 

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