Used Hydrogen Peroxide for Removing Metal Stains - Results

[smallpooldad]

Firstly I read this post in the "Deep End" on this forum:

http://www.troublefreepool.com/using-hydrogen-peroxide-for-removing-metal-stains-t41199.html

I found it interesting and decided to give it a go as ChemGeek found no real issues with it

And a word of warning I would like ChemGeek to review what I have written and make comments on what he likes and does not like before any of you go charging off and doing it. Just because it worked for me in my particular set of circumstances it may not be appropriate for you.

Please note carefully: my 10,000 gallon pool is 16+ years old non-colored plaster salt water pool. The non-colored part of the warning maybe important, colored plaster can sometimes stain with some chemicals.

A little history follows; before Xmas perhaps late November I did the normal AA treatment for iron substituting a small amount of Hydrogen Peroxide to reduce my chlorine from around 5 to zero instead of using Thiotrine. After the treatment I increased Jack's Magic Purple Stuff to 40 ppm as a base amount from 30 ppm. Since then I have had a much slower accumulation of noticeable iron stains than I normally had in the past. Unfortunately since then we had two separate weeks of very high winds, in excess of 45 mph and as high as 60 mph. This as is normal resulted in the deposit of large amounts of wind born dirt much of which contains volcanic dust (which also contains a fair amount of iron oxide) and organic debris . In those two separate weeks I made sure the sequestrant Jack's Magic Purple Stuff was maintained at 40 ppm.

Despite maintaining the following numbers, small shadows started to appear in the pool particularly in the last few weeks and while not noticeable to those unaccustomed to our pool I noticed them. So I decided to do an iron treatment but based on the above post in the "Deep End" I thought to try out the "Hydrogen Peroxide Method" as it does not affect the pH and as I already keep it at 7.3 to 7.4 anyway it would create less work to re-balance it back from the normal 6.6 to 6.8 that results after the AA treatment. I did lower the pH to 7.2. The numbers before starting looked like this:

Cl 6
pH 7.2 (normally 7.3 to 7.4)
TA 80
CH 350
CyA 80
Salt 3300
Borates 0 (dog)
Temp 70F

Phosphates are well over 20,000 ppb but they are no trouble so long as the Chlorine is kept at 5 or above (max 9) or I have problems getting a pH reading.

After the sunset (to avoid an algae bloom) at around 7pm, turned the SWG to zero percent production and added 126 ozs of 3% Hydrogen Peroxide, which lowered the chlorine from 6ppm to zero. I then added an additional 178 ozs to act as a metal stain remover/oxidizer. The pool pump ran all night, as the pH does not change with Hydrogen Peroxide, I did not have to bypass the heater or remove the in-pool suction cleaner.

In the morning before dawn about 5:30am I added 8 oz of Muriatic acid and two large 184 oz jugs of Chlorine. After two hours with pump and cleaner still running I returned and the pH was 7.3 and the chlorine read 6 ppm. All other numbers remained the same.

Now the results, well the pool looked OK for the most part. The stains that were there were hardly visible to the naked eye but they were very faint so I knew they were there. So I thought OK but not as good as AA. Now 4 days later even the faint stains are nearly impossible to see unless one knows what to look for. Interestingly I have one 16 year old fisheye which I have never replaced, it had a dark greyish/yellow stain on it's movable ball on the underside which was quite noticeable if turned towards the surface, that stain had never been removed by the AA treatment, nor by chlorine shocking, but now the small stain is nearly gone, especially the grey cast; it is now a very faint yellow.

I am not sure why as these four days have gone by it is still cleaning but it is. My guess is that it must have reacted not just with the iron but also with the organics and/or another metal type stain, or it lifts the stains so that the chlorine and sequestrant can do their work better. The temperature was not high and we have not had a lot of sun. I believe that Hydrogen Peroxide breaks down in sunlight, my only guess perhaps, and it is only a guess, is that with a high CyA of 80 it is somewhat shielded from sunlight breakdown, so in non SWG pool with a lower CyA it might breakdown too quickly and more Hydrogen Peroxide might be required.

Note: Virtually no sequestrant was used up in this process when I took a reading four days later.

As the reader might note the temperature was a low 70F, and the Hydrogen Peroxide had only a strength of 3% and I did not use that much deliberately as this was a first attempt. And I did not want to spend a lot of money on replacement chlorine to bring it back up to 5 or 6 ppm, after the normal AA treatment I always use up 6 jugs of chlorine or more until it gets fixed at 5 or 6 ppm, why I do not know.

Nevertheless the results were very good after 4 days, nearly as good as AA and in some ways better, and I am happy. I might go for more Hydrogen Peroxide, maybe twice or three times the strength next time, to see if all the virtually unnoticeable light remaining iron stains can be removed. Nobody else seems to see them except me, in fact my friend thinks I am seeing things that are not there, but they are.

I could not find the 27.5% stuff here in Honolulu at any of the local pool stores. Someone told me a medical supply house may carry it, known as 30% Hydrogen Peroxide . The local industrial chemical supply house has 50 gallon drums of 50% but that is a little over $500, and therefore too expensive.

Finally I still think AA is an excellent quick fix to persons with just iron as an issue, and most probably gets rid of most if not all the iron stains. However if wind born dirt or other unknown stains, not removed by the AA treatment, are also an issue this perhaps is worth doing. Indeed I might mix the two together IF AND ONLY IF Chemgeek thinks that is OK, or do Hydrogen Peroxide on day one and follow with AA a few days later, after rebalancing the water as I have done here.

Hope these results are of interest and of help to those with these issues.

Good Luck but wait for ChemGeek to comment or issue warnings before proceeding, and you may have questions for him.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

That's good news that you report. As for hydrogen peroxide strength, that's irrelevant in terms of what it will do for stains in your pool. All that matters is the concentration of hydrogen peroxide you end up with in the pool. If you use 3% but use 9x more volume of it than 27%, then that is the same thing as using 27%. The only reason to use the more concentrated product is if it is less expensive (per % concentration).

I would just like to note that if one is going to have the chlorine level at zero for an extended period of time, then one should use an algaecide such as Polyquat 60 to prevent algae from growing. Other than that, the procedure you described seems quite reasonable and perhaps if more people try it then we can get a better sense for which kinds of metal stains get removed best by hydrogen peroxide. Iron, copper, silver, manganese, etc.

Thanks again for doing the experiment. This is really the only way we can know for sure that something works regardless of what chemical theory might suggest.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Thank you for your kind reply.

Here is an update as of today (day 5):

There are now NO visible stains not even the "virtually unnoticeable light" stains. So it appears to still be cleaning.

The old "Fish Eye Ball" I removed for inspection again today and the color is now no longer a faint yellow but a very faint off white.

Four smaller than dime size spots created about 3 or 4 months ago by leaves from a unknown tropical tree my neighbor have been removed with Vitamin C tablets. These were visible but only slightly so but they became more apparent over the last few days as the pool has become even lighter in color. They cut the tree down about 2 months ago thank goodness. Nothing stained like that little tree fortunately the leaves very rarely got into the pool as the wind blows 95% of time in the opposite direction and the wind had to be blowing really hard for even a few leaves to reach the pool.

The chemistry numbers I gave in the last post have not changed except for the chlorine has moved from 6 to 8, despite the same 24% output on the SC60 cell, so I will lower that. Run time on the pump is 5 hours. My guess and again only a guess is that the pool is being supplemented in its sanitation by the Hydrogen Peroxide. What do you think might be happening? It could be it also have made the blades a little cleaner and more efficient but there is no way to measure this.

This "Hydrogen Peroxide Method" that I discovered on this great forum with your help to the poster is really impressing me.

The fact that one can do it with only small additions of acid and chlorine and not have to lower the pH where one has to bypass the heater or other copper tubing makes it very feasible for those who cannot bypass their heater.

I forgot to mention when we first opened the pool 16+ years ago we were given a free "Nature2", by our pool plasterer, which we discontinued using after 4 or 6 or so years, cannot remember that far back. We stopped using it based on opinions on this forum as to the potential for staining and the lack of need for it, if chlorine levels and CyA levels are properly maintained. It is possible that the "Fish Eye" is slowly having those stains removed, I believe copper is used in Nature2 and possibly silver although I am not sure of this. In defense of Nature2 they claim their product does not stain and I believe have a no-stain warranty if used correctly, which may not have been the case in those early years, not being aware of this site and it's suggested chemical balances.

I am beginning to ponder the small addition weekly of say 8 ounces of 3% Hydrogen Peroxide to keep the pool as clean as it is now. I will let you know the results in 4 or 5 months as to the whether or not it helped or made a difference.

Hope this helps and once again thank you.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

A thought came to me and so if my neighbor agrees we will proceed.

His SWG 20k gal pool is older than 20 years, the plaster was heavily damaged by black algae over a period of many years which I got rid of for him. Much of the plaster is delaminated and while the pool maintains a FC of 5 and no more algae has grown back we cannot keep the pH at 7.4 or below, when we do this more plaster separates from the walls. the pH is now kept at 7.7. It took me about a month, of daily scubbing every evening with a chlorine puck for me to manually remove all the black algae, the pool was kept at shock level for two or so weeks during this daily scrubbing. I then removed all the iron with the AA method, but as he does not want the expense of a sequestrant nor can we keep the pH at 7.4 or below stains have re-appeared, but no algae. So we are so to speak "Between the Devil and The Deep Blue Sea".

I did this as a welcome home present after his quadruple bypass, he was very happy.

As noted in the above posts when doing this "Hydrogen Peroxide Method" no sequestrant was used up, so it maybe that it is not required in this method. I know that in your post you mentioned that it is required and indeed this most probably is the case but there is a faint outside chance that this is not the case under this method. Obviously this would be a huge saving. So I will experiment as follows if he agrees.

We will initially lower the pool to a pH of 7.2, add twice amount of Hydrogen Peroxide I used as his pool is twice as big volume wise. Add back liquid chlorine the next morning and balance back to a pH of 7.7 and a chlorine level of 5, if after a few days, maybe a week the stains are lifting, we will add 16 oz of Hydrogen Peroxide per week in his 20,000 gallon pool.

I see no harm in trying this method and if the experiment works then I to can raise my pH and eliminate the use of sequestrant. I know it is a long shot.

Unless you see a reason for not trying it I will give it a go and burden the small expense as it will also benefit me.

Please let me know what you think even if you think I am "Nuts" or crazy.

Thank you.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

I forgot to mention when we first opened the pool 16+ years ago we were given a free "Nature2", by our pool plasterer, which we discontinued using after 4 or 6 or so years, cannot remember that far back. We stopped using it based on opinions on this forum as to the potential for staining and the lack of need for it, if chlorine levels and CyA levels are properly maintained. It is possible that the "Fish Eye" is slowly having those stains removed, I believe copper is used in Nature2 and possibly silver although I am not sure of this. In defense of Nature2 they claim their product does not stain and I believe have a no-stain warranty if used correctly, which may not have been the case in those early years, not being aware of this site and it's suggested chemical balances.

I am beginning to ponder the small addition weekly of say 8 ounces of 3% Hydrogen Peroxide to keep the pool as clean as it is now. I will let you know the results in 4 or 5 months as to the whether or not it helped or made a difference.

Nature2 in spas is a combination of silver and zinc ions while for pools it is a combination of copper and silver ions. The key to preventing metal staining from this sort of product is to prevent the pH from getting too high and the metal ion concentration from getting too high. For some metal ion systems a type of sequestrant is used that binds excess metal ions and attempts to inhibit staining and the claim is that the ions are still active for their intended purpose such as algae inhibition, but that is questionable. Copper staining can be green to blue-green to black while silver staining is almost always black (or at least gray).

If you add hydrogen peroxide to a pool with chlorine, all that will happen is that it will react with the chlorine basically acting as a chlorine neutralizer. A complete waste of money. The only way that hydrogen peroxide would help with ongoing metal staining is to have the chlorine level get to zero and have excess hydrogen peroxide remaining so this isn't a "maintenance" kind of activity, or at least not an easy one.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

As noted in the above posts when doing this "Hydrogen Peroxide Method" no sequestrant was used up, so it maybe that it is not required in this method. I know that in your post you mentioned that it is required and indeed this most probably is the case but there is a faint outside chance that this is not the case under this method. Obviously this would be a huge saving. So I will experiment as follows if he agrees.

Hydrogen peroxide is a reducing agent and an oxidizer in the same chemical. Which way it goes depends on what it reacts with. Reducing agents do best at removing iron stains since it reduces the iron in iron oxides from the insoluble ferric form (Fe³⁺) to the soluble ferrous form (Fe²⁺) so that metal sequestrants can bind to them and keep them from getting oxidized again and re-staining. Usually with a copper stain it needs an acid to get rid of it by dissolving the copper oxide back into copper ions so that again the metal sequestrants can bind to them. So I don't see the mechanism where hydrogen peroxide helps with copper stains except for the overall lowering of the pH in the pool which may help to dissolve some metal oxide-hydroxide stains.

What is interesting is that since hydrogen peroxide is an oxidizer as well as a reducing agent, it can oxidize ferrous ions back into ferric ions. I suspect that this may be a slower reaction and that the metal sequestrant binds to the ferrous ions before hydrogen peroxide gets a chance to react. In water without a metal sequestrant, the presence of iron ions will essentially catalyze the degradation of hydrogen peroxide by alternately oxidizing and reducing it as the iron goes back and forth from ferrous to ferric and back again. Also, solid iron exposed to hydrogen peroxide can rust because the hydrogen peroxide is an oxidizer and also breaks down to form hydroxyl radicals as well as oxygen and both of these can oxidize solid iron to form iron oxides (rust). This shouldn't be an issue in pools because you normally don't have raw exposed iron because chlorine will oxidize it (as will oxygen). This is why stainless steel is typically used that has sufficient chromium to form a chromium oxide passivity layer to protect the steel (iron) from rusting.

Since your stains largely appear to be from introduced iron from water sources, I suspect there aren't copper stains. Copper isn't normally found in natural water sources and is instead introduced into pools by corroded heaters if the pH gets quite low or by algaecides or Trichlor tabs containing copper or by copper ion products (either metal copper bars that get oxidized into ions or product additives of copper sulfate). Your initial use of Nature2 certainly introduced copper into the pool, but I suspect you've removed most of that via water dilution over the years. It's the continued introduction of new iron that is likely your primary problem. Iron will stain yellow to red to brown and sometimes to black -- think of all the colors of rust.

By the way, when metal binds to a metal sequestrant, the sequestrant is not "used up". What uses up a sequestrant is having it get oxidized by chlorine. So it's possible that hydrogen peroxide being a weaker oxidizer doesn't break down the sequestrant, but when you put chlorine back into the pool you will be back to the situation of the sequestrant slowly breaking down so that more will need to be added.

If you want to physically remove the metal from your pool then that is tricky to do and we've talked about various techniques such as the CuLator bag and forced precipitation (usually via sodium carbonate) into the filter with subsequent backwashing/cleaning, but none of these is a sure thing and it won't prevent the new introduction of additional iron to the pool.

I find it interesting that you continued to see improvement in the stains after the hydrogen peroxide was removed by adding chlorine. It may be as you say that the hydrogen peroxide got rid of the worst surface layers of iron oxides exposing interior layers to the metal sequestrant that is apparently able to continue to remove the stain. At least that's my best guess of what is going on, but I'm not sure why the chlorine isn't re-oxidizing the iron and forming new stains. Perhaps as you pointed out the iron might be at least partially dislodged so that the sequestrant is able to operate on it even when in ferric form (some sequestrants do hold some ferric, but they bind much more tightly to ferrous).

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Thank you for your quick replies and the very clear explanations for a lay person such as myself.

So maintenance with adding Hydrogen Peroxide would be a waste of time and money if I understand you correctly. Well I am glad I asked and you put me straight.

For information that might help with what is going on I backwashed the filter today, which I had also done just prior to this treatment, the sight glass ran a mid grey dusty color for about a minute, normally it runs cloudy white for about 1 1/2 minutes, both out of a 2 minute backwash run. I do not know if this information can tell you anything about what is going on with this treatment. Normally I backwash once every 4 to 6 weeks, this was last done 6 days prior to today.

Your point about it re-oxidizing scares me as you stated it is possible it could precipitate out we will have to see although I think possibly that mid gray dust I backwashed out today might represent quite a bit of it I hope.

As my water pollution is airborne and not introduced via the municipal water supply I am as you noted kind of stuck with this issue of constant removal and vigilance. And my neighbor is stuck with his stained pool.

In future when I do the "Iron Removal Treatment" I will put excess Hydrogen Peroxide in as I have just done, and an hour later add the Ascorbic Acid.

Thank you for all your help, even though the news about continuing keeping the pH low and keeping sequestrant in the pool is not what I had hoped for, but we live in a real world.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

In future when I do the "Iron Removal Treatment" I will put excess Hydrogen Peroxide in as I have just done, and an hour later add the Ascorbic Acid.

I'm not sure I understand this. Why would you continue to use the Ascorbic Acid if the Hydrogen Peroxide worked so well for you by itself?

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

You are correct, why bother. Just another senior momentary lapse as my grandkids would say.

Bye and Bye that little "Fish Eye" gets better by the day checked early this morning and it looked even better than yesterday.

My neighbor keeps looking over the wall at my pool maybe he will breakdown and start buying some sequestrant. When the stains are not in his pool it looks pretty good and the delamination hardly shows, it is a shame he will not do it.

Now what do I do with 1 lb of Ascorbic Acid, I would give it to him but he needs 1 lb more it to cover 20,000 gallons, plus liquid chlorine to rebalance.

Thank you for the thought.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Did a little research on Hawaii and island of Oahu soils where Honolulu is located as to what might be blowing into the pool. Generally winds blow from the North East about 90% of the time at an average of 16 to 24 mph (Trade Winds).

We live up a mountain facing South West at about 1000 ft. overlooking Diamond Head, the mountain that rises behind us another 1,000 plus feet or so to the North East is forest reserve with much exposed red clay and darker black looking soils. The dust that settles into the pool is mostly red in color. There is far more rain up the mountain than there is in the low lying parts of Honolulu that receive very little, that is why Waikiki Beach is so popular it can be raining nearly everywhere else but the sun will be shining at the beach most of the time.

In the article I have linked to it seems that the general concentration of predominant minerals in order of magnitude goes in this order Aluminum Oxide (Al2O3), Manganese Oxide (MnO), Silicon Dioxide (SiO2), Iron Oxide (Fe2O3), copper(CU) and Nickel (Ni) exist in trace amounts.

The paper is here that you might understand better than I:

http://scholarspace.manoa.hawaii.edu/bitstream/handle/10125/1458/v33...?sequence=1

On page 110 at the bottom the following is stated regarding the island of Oahu. It seems from this statement we maybe getting more iron oxide than manganese oxide in the red dirt but I am not sure:

"By contrast, ferruginous concretions
on the Hawaiian Islands are generally found
in regions of higher rainfall than on the
Schofield Plateau, Oahu [in excess of 2500
mm/year; Walker (1964)], when manganese
would be completely leached from the soil
and iron mobilized and precipitated. This
situation is reflected in high Fe/Mn ratios of
these ferruginous deposits."

Hoping this might help you as regards what minerals we pool owners and servicers might be dealing with on the island of Oahu.

Thank you.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Might you know what is the oxidation potential v of Ascorbic Acid is, I read that Hydrogen Peroxide is 1.8 versus Chlorine at 1.5.

Would a higher oxidation potential, if indeed Hydrogen Peroxide versus Ascorbic Acid is greater, make a big or no difference, and is it logarithmic ? Would adding even more Hydrogen Peroxide, say double what I added after the neutralizing of the Chlorine, been even better? Albeit that I would have needed to add more Chlorine to get back to 5 or 6 FC. What I am asking here is would greater oxidation reduce the potential for iron to fall back out of solution and therefore re-stain the pool.

I also read that if one has borates, which I do not, that adding Hydrogen Peroxide might produce Sodium Perborate, would that be an issue for borate users?

If the Hydrogen Peroxide is oxidizing the Iron (and possibly Manganese) could it be that it is producing large enough clumps of rust, that in combination with the sequestrant I use, it can indeed be removed from the water? I did see that grey dust. I did read, and might have misunderstood, that when two metals are oxidized together they are easier to remove as they clump together.

Hope these questions are not too stupid, but my teachers back in the days when dinosaurs roamed the earth, told me it is OK to ask stupid questions.

Thank you.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

The higher standard reduction potential (ability to oxidize another substance while itself gets reduced) of hydrogen peroxide vs. chlorine is irrelevant (your numbers are correct for that) for getting rid of iron metal stains since you want a reducing agent for that purpose. That is, you want a substance that itself gets oxidized. Hydrogen peroxide goes both ways (I show chlorine first):

HOCl + H⁺ + 2e^- ---> Cl^- + H₂O ..... E₀ = +1.482V
Fe(s) ---> Fe²⁺ + 2e^- ..... E₀ = +0.447V ..... easily oxidized by chlorine or oxygen
Fe²⁺ ---> Fe³⁺ + e^- ..... E₀ = -0.771V ..... can get oxidized by chlorine
H₂O₂ + 2H⁺ + 2e^- ---> 2H₂O ..... E₀ = +1.776V
H₂O₂ ---> O₂ + 2H⁺ + 2e^- ..... E₀ = -0.695V (more like -0.4 in pH neutral water)
Fe³⁺ + e^- ---> Fe²⁺ ..... E₀ = +0.771V ..... can get reduced by hydrogen peroxide

As you can see, hydrogen peroxide is a weak reducing agent but ferric iron wants to become ferrous and is able to do so with hydrogen peroxide. The thing is that the above standard reduction potentials only tell you what is possible, not whether something will actually occur or how fast it will occur (i.e. the reaction rate). One also needs to adjust the potentials for actual concentrations in the water, including pH when you see H⁺ in the equations. Note that when hydrogen peroxide reduces iron, it is net acidic which probably helps break up the iron oxide-hydroxide so similar to ascorbic acid except that this acidity is only released when it reacts as opposed to ascorbic acid which is acidic upon addition to the water.

Adding more hydrogen peroxide to increase its concentration might make the process go a little faster but not more than proportionately at best. However, this extra amount won't have any effect on re-staining because that occurs when there is no hydrogen peroxide around and instead has to do with the metal ion getting released from the metal sequestrant, such as when it breaks down, and then getting oxidized by chlorine.

Any sodium perborate produced from borates and hydrogen peroxide will get reverted back again once you start adding chlorine back to the pool. Also, I don't know how fast the reaction for producing perborate is compared to the other reactions that are going on.

When hydrogen peroxide reduces the ferric iron in iron oxides to ferrous form, it presumably gets bound to the metal sequestrant. It wouldn't precipitate again. On the other hand, it's possible that it gets reoxidized before finding a metal sequestrant and forms a precipitate as a result rather than restaining. All very complex and hard to predict.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Thank you that was very clear, so both types of treatments have their pluses.

I did some further "Googling" and it does appear when Muriatic Acid is added to water that it enhances the ability of Hydrogen Peroxide to oxidize copper, this might be of some benefit to those who suffer from this issue. It appears and I could be wrong that Ascorbic Acid does not, or possibly neither method helps, what are your thoughts on this?

One of best benefits of this method, as I see it, is that the "Hydrogen Peroxide Method" allows those who cannot by pass operating parts of their pool to remove iron, and possibly other metals, due to the low pH of the "Ascorbic Acid (AA) Method" to perform a metal removal treatment.

As regards its ability to oxidize Magnesium, present in our soils, I could not understand the articles as to whether or not it would help by "Googling", might it help?

It does seem from the scientific articles I read that lower pH enhances the ability of Hydrogen Peroxide to oxidize better, but I think you just pointed that out in your reply.

Tested the sequestrant today, Jack's Magic Purple Stuff, interestingly there was a large drop from yesterday's 40 ppm to 32 ppm. We have only very light winds, over the last few days, so it was not caused by dust deposits. It seems to me, and please let me know if I am wrong, that the key to avoiding a precipitation out is to keep a fairly high reserve of sequestrant, more than the 10 to 20 ppm typically recommended, but this might only apply to pools with wind-borne iron issues and not those where the iron is introduced by fill water. I do not understand the sudden large drop in sequestrant, is there an explanation. pH and Chlorine numbers did not change.

Thank you as always for your help.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

I don't see how oxidizing copper helps at all. What you want to do is to dissolve copper oxides so that the copper gets back into solution so it can get captured by a metal sequestrant. This usually involves lowering the pH. For copper, a reducing agent won't help so I wouldn't expect ascorbic acid nor hydrogen peroxide to be helpful here, except from ascorbic acid lowering the pH but of course you can use Muriatic Acid for that purpose.

Yes, the key to preventing re-staining or precipitation of metals is to keep them attached to sequestrant so that means replenishing the sequestrant when it breaks down. I don't know why the concentration of sequestrant would drop unless the pool was getting shocked with higher levels of chlorine.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Thank you for the reply.

I did not raise the level of Chlorine so the sequestrant drop remains a mystery. Fortunately I do not have copper issues but I was interested if it would help, you answered in the negative but it is good to know lowering the pH might.

The pool at least at present is looking good and I think that maintaining enough sequestrant, as you mentioned, is key to lengthening the time before another metal removal treatment is necessary. The higher amounts of 30 ppm and 40 ppm seemed to have helped quite a bit but eventually it does need treatment. In my case and this may not be the case for others who do not have wind-borne iron 40 ppm it is a significant improvement over 20 ppm, I may even try 50 ppm.

I think I am done asking you questions. I like the "Hydrogen Peroxide Method" because it is so easy and relatively inexpensive to do and removed some stains the AA method could not, but the AA seems very as good as well. I may just alternate in the future.

Thank you for all the time you have spent on this.

 

[smallpooldad]

Lg Sequestrant Drop Mystery Using Hydogen Peroxide Solved

I think I might have solved the large sequestrant drop mystery using "The Hydrogen Peroxide Method to Remove Stains".

In my previous post I mentioned that at that time a large drop occurred "from yesterday's 40 ppm to 32 ppm." Chem Geek wrote in response "I don't know why the concentration of sequestrant would drop unless the pool was getting shocked with higher levels of chlorine." This time the drop went from 100 ppm of sequestrant to around 75 ppm.

The post is "Used Hydrogen Peroxide for Removing Metal Stains - Results":

http://www.troublefreepool.com/used-hydrogen-peroxide-for-removing-metal-stains-results-t56485.html

Topics merged. Please keep everything on a single topic or question together in one place. JasonLion

The pool did not get shocked.

But last night, in my never ending quest to win the "Pool Geek (see Fool) of The Year Award", I thought well tomorrow I am off why not start with a true baseline to see how long the pool will last without an iron treatment if I do both "The Hydrogen Peroxide Method to Remove Stains" and "The Ascorbic Acid Method to Remove Stains".

This I did after sunset at around 7pm, allowing 2 hours for 12 bottles of the 3% Walmart Hydrogen Peroxide to mix with the water, cost around 98 cents for one 32 oz bottle in Honolulu. It is important to do it after sunset as Hydrogen Peroxide losses strength in sunlight.

Then as I was adding 1 lb of AA I bypassed the heat pump, mixed the AA in 4 batches in a 3 gallon bucket and poured it into the pool with the pump running with the suction side pool cleaner removed. Pump ran all night and will run until 4 pm today.

At 5am, before sunrise, I added 3 x 184 oz of Walmart Regular Bleach, and no acid. Took the dog for a long walk and returned at 8:00 am. The pH read 7.5 -7.6, and the Chlorine read 8.0, then added 10 oz of Muriatic Acid. Then took another reading one hour later, pH read 7.1, and the Chlorine still read 8.0.

At this time I decided to re-introduce the suction side cleaner but noticed the pressure had increased a lot so decided to backwash (2 minutes) and rinse (45 seconds) the filter. The filter discharged a large amount of white dust. This afternoon at 1:30 pm the pressure had risen again so I backwashed and rinsed the filter again. As before the filter discharged a large amount of white dust. Took a sequestrant reading and it had dropped from 100 to 75 ppm.

I believe, but am not sure, that this whitish dust to be the removal of calcium scaling. If all I had done was remove iron of which there was virtually none to remove I doubt whether there would be so much whitish dust and such a large drop in sequestrant.

The last time the pool got an acid wash was over 14 years ago, and only in the last 6 or so years have I followed the instructions as to balance on this forum and then not always as well as I should have, I do now. Therefore I believe that over the many years not only have I had problems with iron but also calcium scaling has built up on the walls.

The Hydrogen Peroxide helped in the first treatment with the calcium scaling and because this second treatment occurred at a much lower pH (maybe around 6.6 to 6.8), and maybe possibly because of a higher sequestrant level the resulting removal of calcium scaling was greater.

As Chem Geek, in the previous post, mentioned it would be great if others could confirm these results to see if indeed it does do a good job on calcium scaling, or other mineral staining.

So it seems to me the AA treatment might be the best for Iron, and the HP treatment in combination with the AA better for calcium scaling than just a pure HP treatment, because of the lower pH.

One advantage of using HP with the AA treatment even if it is just for lowering chlorine levels to zero and not adding additional HP for cleaning is that it works much faster at lowering the chlorine to zero than Thiotrine, and I do not seem to add back as much Chlorine. By this I mean that in our pool using just Thiotrine and not HP I would have used 6 jugs of Walmart 184 oz Regular Bleach, why I do not know, but I used to struggle to re-establish chlorine levels. Also I do not need to put in Algaecide 60, as HP is a sanitizer.

And yes the pool looks quite a bit lighter overall. I suppose that I had become accustomed to an albeit lightly scaled color. Thinking that this is the way it must be for the color, due to 16+ plus years of constant staining. Boy was I ever wrong, fortunately so. And most fortunate to have read on this site someone else's experience using Hydrogen Peroxide.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

Additional Info:

I should not have added the Muriatic Acid, based on my pH test the morning after the treatment which read 7.5-7.6, as later that day the pH level dropped to below 7.0 after I had backwashed out twice. I am guessing that possibly what I thought was calcium in the backwash was acting as a pH buffer. Adding back 1 box of Borax brought the level back to 7.3.

Any ideas why this might have occurred.

Thank you.

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Last night added 336 ozs of Hydrogen Peroxide, after lowering pH to 7.0, as I believe the treatment does better at a lower pH than 7.3. Ran pump all night, this morning phosphates measured about 2,500 down from 10,000.

This time however the filter pressure did not increase in pressure, performed a 1 minute backwash and 30 second rinse virtually nothing was removed, no white dust like the last time.

The only other number that changed was calcium which had dropped to 300 ppm, about 50 -75 ppm from where I had originally started, sequestrant levels remained the same as after the last treatment. My assumption, and I might be wrong, is that on the prior two treatments I was removing calcium stains from the walls and this time while a small amount might also have been removed from the walls the Hydrogen Peroxide actually oxidized calcium in the water.

So my own observation is that Hydrogen Peroxide, as you stated might be quite selective as to what it oxidizes. It seems to do a very good job on calcium staining and on removing phosphates (what kind nobody seems to know), but as far as iron stains it is most probably not anywhere near as effective as Ascorbic Acid.

One other thing it is not good at removing is organic stains, unlike chlorine, the reason I know this is we have very large slugs and occasionally large African Snails which fall into the pool and have done so in the last week , I usually have to remove these stains by running a puck over them. I left the stains in the pool on purpose to see if they get removed by the Hydrogen Peroxide, they do not. So it seems that if organic stains were a problem overall in the pool, and not just in a few spots as is my case, shocking with chlorine might be better.

A final thought, I think that as you stated the amount of Hydrogen Peroxide used for each treatment is safe it therefore might not be a good idea to increase the amount. Better to keep re-doing the treatment until no more calcium scaling is being deposited into the filter (when backwashing shows clear from the beginning), or phosphates are at a level one feels comfortable with.

I am done with my treatments so will not have anything further to add, unless you have a question.

Thank you for all the help and comments you have given me.

 

[chem geek]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

So I presume that some of the continued fading of older yellowish stains was removal calcium carbonate scaling and not iron staining? Is that why you think that the hydrogen peroxide is better for removing calcium scale while ascorbic acid is better for iron stains?

 

[smallpooldad]

Re: Used Hydrogen Peroxide for Removing Metal Stains - Resul

chem geek,

Yes that is what I believe. It might be that when doing an AA treatment that calcium scaling is also removed but some or all of it gets re-deposited, is that a possibility? With Hydrogen Peroxide for some reason the calcium goes to the filter thank goodness. Do you think any iron is getting bound to the calcium in the filter and is also being flushed out with the backwash?

Looking forward to your thoughts on this idea.

Thank you.