Identifying Metal That Has Already Plated Out

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Michael1

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May 3, 2015
206
Moorpark, CA
I have an even staining on my pool that turns my blue plaster slightly yellowish. I have had small dark stains that I thought were organic, and put ascorbic acid tablets on them with good success. The immediate area were I have put the tablet had also ridded the area of the yellowish appearance. I think I can really blue up the pool with ascorbic acid.

My concern is I don't know if the yellowish appearance is just organic staining due to age (I have only been in the house for less than a year), or from a metal such as iron. Some people swear if ascorbic acid gets rid of a stain, it has to be iron. Others say they have gotten rid of stubborn organic stains with ascorbic acid. I don't want to use $500 worth of metal sequesterant a year, and there really isn't metal there. You have to add sequesterant on a continual basis. I tested the water for iron and copper at the pool store, and it was zero.

If I do an ascorbic acid treatment, and test the water for metals at that time (after the stains are lifted), could I confirm whether the stains are metals?

Michael
 
My pool tested 0 for iron yet I got iron stains. Everything I read in your post points to iron stains.

Try placing a tri-chlor tab on the stained surface for a few minutes. If it is organic, it will noticeably lighten........I don't think it will - demonstrating your stains are likely iron.
Others say they have gotten rid of stubborn organic stains with ascorbic acid.
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Who said that?
 
Michael, iron testing in these cases seem to be highly unreliable and mild staining can happen over time from very low levels. In our collective experience here, what you are describing conforms exactly with mild iron staining.

In your shoes I would perform the AA treatment, which uses sequestrant anyway (testing for iron if you like before adding the sequestrant) and then if it still tests zero, wait and see whether or not you end up needing to replenish the sequestrant.

You may be fine, or you may notice yellowing a few weeks later...in particular, watch your plastic parts, (eg skimmer face) as they will turn bright white with AA, and then begin to discolor if there's free iron releasing.

I don't recall if in previous posts you ever answered my question about whether you're on well water or city water (forgive me if I've simply forgotten). If you're on well water, test IT for iron before other chemicals are involved for more accuracy.

But in the end, if your pool looks better after an AA treatment, then you've had metal staining, and you will need to some degree or another maintain the sequestrant or the staining WILL come back...the question is when.

For some folks, that's a few bottles a year. For others, its a case.

In my case, it was a case, but even with 2 ppm iron, I didn't spent half of 500 for my 6 month season....more like 160 for a case of metal magic from poolgeek.com (best price, free shipping on a case.)

So AA lifts stains, sequestrant "holds" the metal, but wears off, and the rest depends on the profile of your well or city water and ergo the trace amounts added or the effect of dilution, plus the ph of your pool water (high ph oxidizes the metal, causing it to stain...a ph around 7.2 will to some extent help control the pace of staining if you can maintain your plaster in the lower ph parameter).

From this general formula you can gather the best long term handling of metals is metal free additions of water...in my case, it meant using a water softener on be outdoor spigot to mostly control the addition of more iron...I hardly use more than a few bottles of sequestrant a season now as a result of a two-year quest in this regard ... I have a sand filter, so its the backwashing and water replacement, etc. that helps...evaporation alone will not do it ;)

Another option for those on well is a complete water change, trucking in metal free water. But with evaporation and then subsequent additions from a well, over time you would get back to a higher metal concentration if there's metal in your source water.

Hope that gives you some strategies to ponder. Iron is a PITA and I'm sorry to say there are no real shortcuts here ;)
 
I feel your pain! Been battling iron stains for 2 yrs with no idea how I suddenly got them since I use TFP exclusively! No iron in fill water. My whole liner has a yellow tint. I've done AA treatments and liner looks beautiful. I use seqestrants but as soon as I raise FC to the recommended level the stains come right back after a couple of weeks. Been a vicious cycle! Before opening this year I will do another AA treatment then try some scum bags, paper towels etc in my skimmer. I've read it helps. I will follow your thread and also let you know if I find a miracle cure! Good luck!
 
Thanks everyone for the input.

Dave, trichlor tabs did not do anything to these dark stains.

Here is an example of someone who removed organic stains with ascorbic acid that trichlor would not completely remove. See post #3.

http://www.troublefreepool.com/threads/29253-Question-regarding-leaf-stain-removal

Swampwomen, thanks for the detailed response. Now that you mention it, the white portion of my pool sweep does look yellow. I am on city water, so I can't think of where iron would have entered the water. The good news is lately none of the dark stains that were removed by the Vitamin C tablets have returned. That was not the case a number of months ago. I have changed about 40% of the water since then. I was new to TFP, so my water wasn't well stabilized at that point. Also the area that was lightened by the Vitamin C appears to be staying light.

Smforte, sometime stains can be a real battle. I'm glad I got the jumbo bottle of Vitamin C.:D

Here is one more question for everyone. Is there a minimum water temperature for the ascorbic acid treatment? My water is 58 degrees right now.
 
Michael, it will work more slowly at that temp...in my experience anyway. It works best over 70 degrees. I did do a treatment once in cold water and simply łeft it longer before bringing the FC back up, eg. 2 days instead of 1. It still worked, just not as fast.

With city water, you likely won't have to sequester much in terms of frequency after your treatment. Occasionally some municipalities will have increases in iron -- eg they switch to different water sources in peak demand and so on...but its usually a very low amount. Other sources of iron include leaching granite or flagstone, fertilizers and soils. These trace amounts can build up over years and my recollection was that when you purchased the pool it had very high cya, which might also have meant the water was not likely changed for a very long time -- not that it needs to be....just a possible explanation of the staining despite city water.

Regarding using stain remover for leaves in that post...leaves and organic matter like worms do in fact have iron components along with tannin when they decompose. My best guess is that is what was left behind on those stains that the AA in the stain remover removed in that thread ;)
 
Swampwoman, thanks for the advice. You are correct. The water hadn't apparently been changed in years even though they were using pucks. The pool is a lot happier now that I have changed some of the water, and the CYA is down to 60. Hopefully, I changed out some of the iron, too.

I think I'll give it a try in cold water. It's not a bad time of year to do this, since the sun and cold water don't produce algae as much, although it will take a while for the chlorine to drop.
 
Michael1 said:
Swampwoman, thanks for the advice. You are correct. The water hadn't apparently been changed in years even though they were using pucks. The pool is a lot happier now that I have changed some of the water, and the CYA is down to 60. Hopefully, I changed out some of the iron, too.

I think I'll give it a try in cold water. It's not a bad time of year to do this, since the sun and cold water don't produce algae as much, although it will take a while for the chlorine to drop.
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Louisiana pool over here, similar temps to you (water at 55deg currently), and I'm in the process of finishing up an AA treatment. We have a lot of trees around the pool, so doing it while they're all leafless was my logic for doing it now along with some polyquat to reduce the possibility of an algae bloom. The results are striking after 24 hours and, hoping I can bring my levels back in check to keep it this way. I say temps like we're seeing now are fine for this based on my observation over the past day or so. Today I'm starting to raise the pH back and maybe tomorrow I'll be ready to start adding chlorine back to the pool.
 
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