Ascorbic acid treatment for stains, which sequestering agent to use?

[MountainStone]

I have stains on the bottom and sides of my pool and on the advice of PoolDoc I dropped a vitamin C tablet on one of the stains. The tablet removed the portion of the stain that it touched. This tells me that the stains are metal and I need to remove them using the ascorbic acid treatment. I read the sticky at the top of this forum and the process seems pretty simple, except the author mentions that a sequestration agent is used but not what kind/name of the sequestration agent. Is there a preferred type/brand? If not, can I ask my local pool supply store to provide 'sequestration agent' and be confident he/she will sell me the correct chemical?

Also, is the sequestration agent filtered out into my cartridge filter? Should I clean the filter after the process or does the sequestration agent hold the metals in suspension indefinitely?

Thanx!

[PoolDoc]

I'm working on a chemical sources page, like the new test kit page (), but haven't finished it.

The sequestrant is HEDP. It's widely available BUT in mystery blends. So get this one -- EXACTLY this one, from Amazon:

KemTek 20% HEDP @ Amazon

Usually, I say "or one like it" -- but in this case, get this one EXACTLY. It's the only HEDP product where I know the exact ingredients. I'll edit the Vitamin C sticky to include this.

You may get ascorbic acid (Vitamin C) at Amazon as well.

Also, there's a problem with the Vitamin C treatment: it lifts the stains OFF the surface, and put's them BACK into the pool water. But, the metals can RESTAIN your pool. We're seeing some indication that this product works as advertised. If it does, it will remove the metals from your pool water

CuLator - 1.5 ppm unit
CuLator - 4 ppm unit

If you get one of these, do NOT start using them till AFTER you've 'lifted' the stains.

Also, the CuLater package will probably NOT be used up when you're done, especially if you get the higher capacity one. You can probably remove it, and store it in your fridge in DISTILLED water, and then reuse later in the season. (I'm gonna check and see, but Periodic Products won't like that approach, so I'll have to be careful how I ask.)

--- I'm gonna update the Vitamin C sticky and the add some more comments to this thread --

[MountainStone]

Thanks for the reply and the recommendation, Doc.

I thought the purpose of the sequestering agent was to sequester the metals in a dissolved state, preventing them from redepositing as stains. Are you saying that is not the purpose of the agent, or that the agent does not do the job completely/permanently?

Should I skip the sequestering agent and only use the CuLator? If so, should I test my water to determine what ppm of metals I have and buy the appropriate CuLator or just purchase the 4ppm version?

Thanx again!

[PoolDoc]

1. Sequestering / chelating agents are marketed as if their action was complete and permanent, when in fact it's neither complete OR permanent. They TEMPORARILY solubilize metals, but once they break down, metals return to their active form and are EITHER removed from the water OR appear as new or returning stains.

2. Most methods of metal removal don't work with chelated metals; CuLater claims to do so.

3. The CuLater -- to the degree that it works, and we *think* but do not know that it does -- ONLY removes metals in the water; it has no effect on stains.

So, if you chose to pursue it, what I'm proposing is a 3-step process
1. Re-dissolve the stains -- you pretty much can't have chlorine in the pool during this period
2. Chelate them, so the metals REMAIN in the water when begin chlorinating again, and don't re-stain the pool. (Temporary state)
3. REMOVE them with CuLator, or another method

None of what you need to do is difficult, but it is picky: you have to do the right thing in the right order, to make it work. I anticipate that you'll need to spend about $150 + a K-2006 (if you don't have one), from start to finish. If you want to go ahead, I'll 'whip' up a recipe and give you an order list.

You asked, above:

Is there a preferred type/brand? If not, can I ask my local pool supply store to provide 'sequestration agent' and be confident he/she will sell me the correct chemical?

Your question pretty much nails the problem we've had here: you can NOT trust the pool store to give you the right chemical. Not only do they not know (usually) what the right chemical is, the chemical companies generally make it difficult to find out exactly what's in "Metal Free" or "Metal Magic" or whatever. We've run into one case this year, with Natural Chemistry's "Metal Free", in which they have COMPLETELY changed ingredients. Same container; same basic instructions; same sales claims --- completely different ingredients, neither of which -- by the way -- are very desirable ones!

To do this correctly, you need to use the right chemicals at each step -- the brand doesn't matter, but the chemicals do. We haven't been able to do what I'm proposing, because we haven't been able to make sure people got EXACTLY the right things. Now that Amazon is selling a wide range of pool supplies, I can give you a link to THIS, and THIS and THIS, allowing me to create a fairly exact recipe. The head chemist at Kem-Tek not only knows of PoolForum, but likes it and is willing to tell me EXACTLY what's in his blends, so I can know how to use them.

So, I'm ready to go . . . if you are! I really, really would like it, if you could take pictures as you went through this. In one sense, this is an experiment. I know that it will 'work', but not how well. My guess is, you'll be able to remove most, but not 100% of the stains.

If you are willing to pursue this, I also want to get Chem_Geek (who knows more pool chemistry, analytically, than I do, or for that matter, than anyone else in the world -- literally!) and Marie (who has helped many people here with stains) to sit in on this thread. You'll be the first case of a new, precise, stain removal process!

[MountainStone]

Doc,

I'm willing to attempt this following your direction and document the process. My two concerns are that I don't want the pool to be out of service for too long (we're anxious to get in our first pool and the weather is rapidly warming here in Vegas) and I do want to eventually eliminate all the stains in my shiny blue fiberglass pool. You say your guess is that I'll not be able to remove 100% of the stains with your process and I can live with that through this experiment, but I do want to find a way to remove them all before the end of the season. I recently received my K-2006 upon your recommendation, and am currently keeping my pH low and aerating to lower my TA. My calcium is at 600ppm and will rise due to high calcium in my fill water and high evaporation rate (dunno if that makes any difference). I'm willing to start whenever you are, again provided that the pool is not out of service for an extended period.

[PoolDoc]

Are y'all not swimming now? I just looked at your weather forecast, and it's showing lows in the 70's and highs in the 90's for the next week.

As far as 'out of service' -- I would only anticipate it being out of service for a couple of days while you were treating it with the ascorbic acid. None of the other things would be incompatible with swimming.

Let me contact Chem_Geek and Marie, and also, I need to get the chemical info page posted, so I can direct you to the exact products you need.

High evaporation + high calcium fill will absolutely tend to cause a climbing calcium level. I'm posting your test results from your earlier thread here, for reference in this thread:

Fill water:
FC = 1.2 ppm
CC = .2 ppm
pH = 7.6
TA = 140 ppm
CH = 270 ppm

Pool water:
FC = 4.2 ppm
CC = .2 ppm
pH = 7.8 (acid demand test yielded 1 drop to bring to 7.6)
TA = 180 ppm
CH = 600 ppm (tested this 4 times, once at 25ml and 3 times at 10ml)
CYA = 90 ppm

If you could, go ahead and take pictures of your pool, and your equipment, and send them to me (poolforum@gmail.com) for a reference post.

[MountainStone]

Doc,

We have yet to get in the pool though we are quite anxious to try it out. Water temp hit 70 yesterday for the first time and the forecast calls for highs in the 90s the next few days. The sunshine is a physical force here in the desert, so we may attempt a short dip at midday this weekend; the water's just been a little too cold up to this point.

I'm fine with no swimming for a couple days; glad that is no barrier. I mentioned the high calcium because I didn't know if it would factor into your prescription. My test results today are pH: 7.2 and TA: 120ppm. I am adding dry acid every day to keep pH low and aerating to bring down the TA. I currently use trichlor in a floater for sanitation.

I sent photos of my pool and equipment to the address you listed.

[chem geek]

As far as 'out of service' -- I would only anticipate it being out of service for a couple of days while you were treating it with the ascorbic acid. None of the other things would be incompatible with swimming.

Let me contact Chem_Geek and Marie, and also, I need to get the chemical info page posted, so I can direct you to the exact products you need.

You only need to stay out of the pool during the time the ascorbic acid is working to remove the metal stains. The reason is that ascrobic acid will remove all the chlorine in the pool so it will be unsanitary during that time. Usually the stains will get removed within a day or two, sometimes in a matter of hours (depends on how old the stains are). Ascorbic acid works better for iron stains; not as much for copper stains.

So you would let the chlorine drop somewhat on its own before adding the ascorbic acid so you don't waste so much money on having ascorbic acid just get rid of the chlorine (you wouldn't let the chlorine drop much below Ben's minimum FC chart, but you can let it certainly get to or slightly below that minimum). If your pH isn't somewhat on the lower side (definitely below 7.5) then lower it. Then add enough ascorbic acid to get rid of the FC and have extra left over. One pound of ascorbic acid in 10,000 gallons gets rid of 5 ppm FC. So any excess beyond the amount needed to get rid of the chlorine will be used to reduce the metal stains and get them into the pool water.

The ascorbic acid will also lower the pH more which is part of how it works (it's also a reducing agent). Once the stains are gone then you'll add a metal sequestrant that has HEDP such as Ben referred to. That will keep it in solution at least for some time -- it breaks down over weeks from chlorine, but fortunately not as quickly as EDTA-based metal sequestrants that break down in days to 1 week and create a much higher chlorine demand. After you've added the metal sequestrant and had it circulate for an hour or so, you slowly add chlorine and can also slowly raise the pH over time. You can swim as soon as you've got the minimum FC level from Ben's chart for your CYA level. If the pH is still on the low side, that's OK for swimming since it's not horribly low.

As for the CuLator®, you can add that packet anytime into your skimmer, but normally would add it after you've added the metal sequestrant. The CuLator isn't fast, but will remove (absorb) metals even when bound to metal sequestrant. It will take weeks of circulation to remove most of the metal and if there is a lot of it then it could take more than one bag though as Ben points out if there isn't very much then a bag could be used again at another time.

[MountainStone]

Thanks very much for joining this thread, Chem Geek! You make it sound pretty easy, which builds my confidence (new pool and still afraid I'll 'break' it). At this point I'm just waiting for Ben to give me his step-by-step instructions, bill of materials, and guidelines for documentation.

[PoolDoc]

Here are the photos:











1.5HP uprate motor


PRA6F-148L






Enhanced view of stain


StaRite PXC150 filter


Enhanced view of stain