Ascorbic Treatment to rid Pool of metal stains

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buddywiser

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May 23, 2007
98
Morgantown, WV
JasonLion said:
Ascorbic acid is way way way milder than an acid wash. There won't be any plaster etching, though the metals coming off can change the texture of the surface.

As far as the filter goes, normally any iron in the filter would be removed. However, there are rare cases where something else happens. With a lot of iron in the water, stains can form very quickly under the right conditions. Remember, this isn't at all common. The whole goal of the treatment is to avoid those conditions. However, if something goes seriously wrong, you can deposit iron very quickly. If that happens inside the filter, the filter media can be destroyed. If that happens just about anywhere else then you are back where you started, which isn't good but also isn't terrible.

This is just the information I was looking for. I ordered some AA from 3 weeks ago and removed my stain. Then I put in some sequestrant. My pH was consistently around 7.2, but 2 days ago, the stains came back out of nowhere. I checked the pH and it was 7.6. So now I guess it's back to the drawing board :|
 

buddywiser

LifeTime Supporter
May 23, 2007
98
Morgantown, WV
By the way, does anyone know the shelf like of AA? The more you buy, the better the deal. I'm also thinking about trying the Citric Acid as mentioned in the OP's post since it's way cheaper.
 

oldogface

LifeTime Supporter
Mar 22, 2010
25
Ridgeway, SC
Just to be clear... I was told earlier by a pool maintenance guy how to do the AA treatment with one exception to as stated here.... his comment was to run the filter in the "FILTER" position after adding the Metal Out, and then "Backwash" to remove the metal from the filter (and water?), followed by DE replenishment... from the preceding, I'm assuming that's not the case? Would be good, because I've been going through DE like crazy!
 

JasonLion

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oldogface, welcome to TFP!

There are tradeoffs about leaving the filter in filter mode. On the negative side, it isn't likely, but the metals can deposit in the filter heavily enough to destroy the filter media (grids in your case). On the positive side, if some metals do deposit, but not too much, you can then backwash them out and be rid of them permanently. It actually isn't all that likely that any metals will accumulate in the filter, so most of the time this doesn't matter.
 

platooka

New member
Aug 9, 2010
2
Hi all,

Newbie here...just wondering if its OK to lower the PH to the levels indicated in this thread even if you have a heater hooked up to the pool. Will the low PH not damage the heat exchanger and result in more metals entering the water?

Thanks in advance...
 

JasonLion

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A copper heat exchanger is totally fine for any period of time down to a PH of about 7.0, and won't even notice a week or two at 6.6 or 6.8, though a couple of years at 6.6 or a few weeks at 4.0 would be a problem.

A standard AA treatment can usually be done with the PH at 7.0 or higher, and if you go down a little too low by accident for a couple of days it isn't a big deal at all.
 

platooka

New member
Aug 9, 2010
2
Great, thanks for the reply...and great site btw. I think I'm going to give it a shot as I had some copper in the pool which seems to have resulted in blue-ish staining on the pebble tec across most of the pool. Also, has anyone heard of a product called CuLator from a company called periodic products (www.periodicproducts.com)? Seems it claims to actually 'remove' metal from water. Thinking I might try it out along with the ascorbic acid as its one of the treatments they recommend for removing metal stains.
 

JasonLion

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ProTeam's Metal Magic and Jack's Magic the Pink Stuff (regular), the Blue Stuff (fresh plaster), and the Purple Stuff (SWG) are some of the top sequestrants. You can also find many other brands with similar products, some of which are noticeably less expensive. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective.
 

JasonLion

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DLSDO said:
I did not lower my FC
I did't notice this at the time, but this is a bad idea. Chlorine and AA destroy each other quite quickly, before the AA has any useful effect, so not lowering your FC level is like throwing away half your AA. AA is too expensive for that to be a good idea. It won't stop the treatment from working, it just makes you use more AA than you otherwise would have needed.
 

michmike

LifeTime Supporter
Apr 11, 2011
105
Houston, TX, USA
mbar said:
Here are the directions to use Ascorbic acid to rid your pool of metal stains:

Here is the ascorbic treatment:

Take your chlorine down to 0, if there is chlorine in the water it won't hurt, it will just eat up the ascorbic acid, so you will need more to get rid of the stains. You can add poyquat 60 per directions on the bottle to avoid getting algae while the chlorine is low.
You will need about a half to one pound of ascorbic acid per 10,000 gal. I like to go lighter on it and see if all the stains lift off before adding more.

Put the filter on circulate.
Use a cup and go around the perimeter of the pool and drop it down the sides as you go.
Let the ascorbic acid circulate for 1/2 hour. You will be amazed how the stain just disappears before your eyes.

If the stain is not all gone, leave the filter in circulate and add more ascorbic acid close to where you still see stain. Leave it in circulate until all of the stain is gone. (add more ascorbic acid if it circulates for 1/2 hour and there is still stain)

When the stain is gone, add enough sequestering agent for the volume of your pool - more is better than not enough.

Put the filter back on filter and leave it on 24/7.

The ascorbic acid will bring your ph down, and sometimes the alkalinity. After 24 hours you can start to rebalance the water. Bring up your ph and alkalinity, - use arm and hammer washing soda first, it will raise both ph and alk. Make sure you test in between, because you don't want your ph to go any higher than 7.2. If your alkalinity is in range, and you still need to raise your ph, use Borax to take it up to no higher than 7.2. You can start to bring up your chlorine. You want to do this slowly. It will take a lot of chlorine - I prefer to use bleach only at this time, and try to take it up to your minimum chlorine for your cya according to the "best guess chart" . As you slowly raise the chlorine, watch for stains starting to form. If you see stains, make sure the ph is no higher than 7.2, and add more sequestering agent. You should see the stain lift in a couple of hours. Do not shock! Do not shock for at least 2 weeks! Make sure you keep your ph low for (7.2) for a week or two - it won't be hard because the ascorbic acid and sequestering agnet will help it stay low. Once your chlorine starts to hold, it means that you have used up the ascorbic acid in the water and it will be easy to rebalance the pool back to your regular parameters.

Here are two important notes: High ph along with high chlorine will precipitate any metals that are not sequestered out of the water and on to the surface of the pool again. If this happens take the ph back down to 7, or 7.2 and add more sequestering agent. This should lift the stain off. You can add polyquat 60 to the water before starting the stain treatment to avoid getting algae while the chlorine is low.

Here are two links to buy ascorbic acid:

http://www.msm-msm.com/store/agora.cgi

http://www.chemistrystore.com/Chemicals ... _Acid.html

Since they have really raised the price on Ascorbic acid I tried Citric acid and it worked.Here is a link to citric acid which is cheaper. You will have to use more, and it takes a little longer but it works

http://www.chemistrystore.com/search.cg ... earch2.y=0
Hi there, any idea on what the amount of citric acid needs to be per 10k gallons? in this article it lists the amount for AA only. I found Citric Acid only on ebay (not at whole foods, or any other pool stores) and i want to buy enough.
[[You will need about a half to one pound of ascorbic acid per 10,000 gal. I like to go lighter on it and see if all the stains lift off before adding more]]
 

chem geek

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Mar 28, 2007
12,083
San Rafael, CA USA
One can compare the different reducing agents by comparing their molecular weights:

Ascorbic Acid: 176.12 g/mole
Citric Acid (monohydrate): 210.14 g/mole
Oxalic Acid: 90.03 g/mole

So 1 pound of ascorbic acid is equivalent to 1.2 pounds of citric acid which is equivalent to 0.5 pounds of oxalic acid. [EDIT] NOTE: See this post regarding chlorine oxidizing citric acid and producing chloroform which is a THM. It is preferable not to use citric acid. [END-EDIT]
 

solarboy

Well-known member
Aug 1, 2010
337
Europe
chem geek said:
One can compare the different reducing agents by comparing their molecular weights:

Ascorbic Acid: 176.12 g/mole
Citric Acid (monohydrate): 210.14 g/mole
Oxalic Acid: 90.03 g/mole

So 1 pound of ascorbic acid is equivalent to 1.2 pounds of citric acid which is equivalent to 0.5 pounds of oxalic acid.
Great news ! I can't get ascorbic acid here but I've 5kg of Oxalic (over-ordered) left over from removing iron stains from some oak flooring.
 

Puffin

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Jul 23, 2010
217
Metro Atlanta, Georgia
chem geek said:
So I'm going to be trying this Ascorbic Acid treatment later this month just before closing the pool to get rid of some metal stains that I'm fairly certain are iron. Some are up to 4 years old, so they may not come out so quickly, but we'll see.

I calculated that the one pound of Ascorbic Acid per 10,000 gallons would take almost 5 ppm FC to get rid of (assuming a minimal amount of Ascorbic Acid gets oxidized by the iron) so that's not so very much chlorine to get things back to normal.

I'll let you know how things turn out with my "old" stains -- created from my first year and a half of pool ownership when I used Trichlor pucks in a floating feeder that sometimes "parked" itself near stainless steel bars I have in the pool and rusted the nearby mounts.

I'm curious as to why one doesn't add metal sequestrant before the ascorbic acid. I would think one would want the sequestrant there to capture the metal as it gets reduced and goes into solution. I suppose that the lower pH from the acid is enough to prevent it from falling out of solution again, but would having the sequestrant in the water first be a problem?

Richard
Chemgeek, did you get a chance to do this? How did it go? Did you figure out if adding sequestrant first was a problem?
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
Puffin said:
Chemgeek, did you get a chance to do this? How did it go? Did you figure out if adding sequestrant first was a problem?
So I was able to get rid of the general yellowing mostly by keeping the pH lower (i.e. before adding ascorbic acid), and the ascorbic acid did somewhat lighten the oldest small dark stains but did not completely get rid of them. I think they are just too old and more deeply embedded into the plaster surface at this point. They are small and not too numerous so it's not a big deal so I'll just live with them. The general yellowing doesn't happen unless the pH gets to 8.0 or higher.

As a test and for possible prevention since some of my stainless steel bar mounts that were initially attacked by Trichlor are still slowly rusting (I think the mounts aren't so "stainless" as they appear much duller than the bars themselves which are very shiny), I've been using CuLator, but I haven't noticed any color change in the bag and it's been a few weeks since I added the bag. I'll leave it in for the season and then open up the bag and see if there is any color change since that indicates absorbed metals (most will color the pellets in the bag). Another test will be to see if the yellowing returns with the pH getting higher (8.0 or so) because if it doesn't, then that may mean that the CuLator physically removed metal ions that would otherwise yellow the plaster. We'll see.

As for using citric or oxalic acids, note that they may not work quite the same as ascorbic acid. They are all reducing agents, but may vary in their effectiveness to remove metal stains. People have settled on ascorbic acid because it seems to work more effectively than citric acid though it is more expensive. Oxalic acid has a higher toxicity profile (so just be careful not to get it on your hands or inhale dust) though it's still less hazardous than some other chemicals we use for the pool. The nice thing about oxalic acid is that chlorine will oxidize it to carbon dioxide whereas ascorbic and citric acids will leave some soluble organic remnants (though the amount you use is small so not a problem).
 

DHinNC

Active member
Apr 26, 2007
28
Ok, so I did the AA treatment Sunday and the stains disapeared just like it says in the instructions given here. After adding ~2 lbs. of the Abscorbic Acid and a bottle of sequestrant the test results showed- Total chlorine = 0 ph = 6.8.

24 hours later I was ready to add sufficient quantity of Arm & Hammer washing soda to raise ph, but when I tested ph was bac up to 7.2, but total alkalinity was only 30.

Question- Should I risk the ph going higher than 7.2 while trying to raise the TA to around 60 or just watch the ph over the next couple of days before I turn the chlorine generator back on? By the way- the water and pool are crystal clear! The AA treatment is amazing!

Thanks for posting great information on this forum!
 
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