Copper staining -- need advice on removal

Hi all,

I made the big mistake of adding some Clorox Xtra Blue granular shock to my pool which I believe has contributed to raised copper level in my pool and staining all over my vinyl liner. Lesson learned!

Here are my test results, using TF-100
FC 17
TC .5
PH 7.4
TA 80
CH 40
CYA 117

Because I do not have a metal test at home, I look a sample to Leslie's and this is what they found:
Iron 0.1 ppm
Copper 0.3 ppm

24 hours ago I took a sample to Leslie's and the copper was actually at 0.4 ppm. I added 33.9 oz of Metal Free to the pool about 5 p.m. last night (almost 24 hours ago), and the level went from 0.4 to 0.3 today. I backwashed one time this morning.

At this point, the entire liner is stained, and no amount of brushing is changing it. You can see along the wrinkles on the liner at the bottom of the pool where the liner is still blue. (See photos attached) Otherwise the pool is clear. I mean, it is not horrible, but the color is off for sure.

Leslie's is recommending acsorbic acid for the stain removal and another bottle of the Metal Free. I feel like I have a good handle on my numbers, but not sure what order to approach this, and if the acsorbic acid is going to be effective in removing the stains. I started reading about the various kinds of acid treatments, but got overwhelmed. I know I need to lower the copper level, but not sure if any of my other chemistry levels need to change first.

Where do I even start? Thanks for any advice!
 

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JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,272
Tucson, AZ
Ascorbic acid is ineffective against copper stains. They will go from brown to black (ascorbic acid catalyzes the further oxidation of copper from it's initial red/brown color to black). Ascorbic acid is only effective against iron stains.

Before you do anything, I would get a stain id kit from Jack's Magic. It will tell you what the most effective method is for removing the stain. But be warned, if it is copper staining, then the removal process is far more difficult and costly than iron stains. It is likely you will remove the copper and then drain a lot of the pool water to get rid of the copper permanently. Many of the "metal removers" are sold as chemicals that remove metal from the water but that is not true. Most simply chelate metal ions and keep them dissolved in the pool water. Removal of most metals is only permanently and quickly accomplished with water exchange.
 

JamesW

TFP Expert
Mar 2, 2011
20,676
That looks more like iron stains than copper.

Drop a vitamin C tabs on a spot to see what happens.

Did you have a period of time when the TA was zero?
 
OK, I will hold off on the acsorbic acid. I have to run to the drug store anyway, so I will pick up some vitamin C tabs just to test that first.

The PH and TA were very low when we first opened the pool. I'm sorry, I don't have those numbers on me anymore, but they were below the normal range. I added baking soda and both levels raised. I have been using straight liquid chlorine from here on out. I had an old box of the Clorox stuff in the garage and decided to put in three bags of that before we were able to get to the store for liquid chlorine. I have been reading that the Xtra Blue stuff has copper in it, so I have learned my lesson.

I'll order a Jack's Magic ID kit in the meantime and get to work on IDing the stains. I was looking at the test kit and it looks like you need to have your chlorine level pretty low, and the water temp needs to be between 65-70 degrees. Are those hard and fast rules? I'm guessing I am going to need to let my chlorine levels fall a little bit as I wait for the kit anyway.

If it is copper (which the Leslie's test indicates I have presence of copper) would adding more Metal Magic make much of a difference? It looks like what you're saying is that water removal/replacement is going to be more effective in the long run. I don't mind doing a partial drain and starting over. In the meantime, is that level of copper (0.3 ppm) not safe to swim in? I have been keeping my kids out of the pool all week as I am trying to figure out what's going on. They're pretty mad at me for that, but we have been getting some occasional rain storms, too.

Thank you all for the advice thus far. This is a new one for me in 19 years of pool ownership, and I am just stumped! Hoping the Jack's Magic will reveal more info!
 

JamesW

TFP Expert
Mar 2, 2011
20,676
If the vitamin C tabs work, an ascorbic acid treatment will probably work.

However, if you really do have high copper, it might make it worse. So, consider that before deciding what to do.

Note: Don't rely too much on the metal tests. They are very unreliable.
 
OK, my husband is stopping to get Vitamin C tabs on the way home and we will do a spot test. I will drop one in and see if it affects the liner. I'll report back on the results.

My FC is 17 right now, which is on the higher end, so I guess we should be good for swimming!

I will start to read up on copper in the case that this isn't iron (and Vitamin C doesn't work).

Thank you again! I really appreciate having a knowledgeable group of folks here. I really hate having to step foot in a pool store, but felt desperate since I didn't have a way of testing for metals.
 
UPDATE: Vitamin C tabs worked! Here’s a before and after when I rubbed a tablet against the liner. It came right off! I have the bottle of ascorbic acid from Leslie’s sitting here now. Would it be safe to add it, or is it recommended checking for other metals with Jack’s Magic first?
 

Attachments

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,272
Tucson, AZ
An ascorbic acid treatment will get the iron off the liner but it will cone back as you raise FC or pH. Clearly you have a lot more iron in the water than 0.1ppm indicated by the pool store.

Do your toilet bowls or fixtures get brown iron stains on the porcelain or is the tank coated with iron scale? If your source water has a lot of iron in it, then the treatment regimen will be more complicated.
 

JamesW

TFP Expert
Mar 2, 2011
20,676
As noted, it will probably work, but the iron and copper will still be in the water and they will eventually stain again.

Maybe have the source water tested for iron.

If you have a lot of copper, there's a chance that the ascorbic acid might cause different stains, even if it removes the iron.
 
I have noticed reddish brown stains in our toilet before, but honestly in the 19 years we have had this pool I have never once had an issue with iron staining the liner. We use the same water source (hose from our house) every year for filling it.

Just a little more backstory to help fill in details ... We opened the pool earlier than normal this year at the end of April since COVID and being home more and all. We actually got a few hot days in early May where the kids got to swim. The chlorine, PH and TA were super low the first week, so I had two bottles of straight 12.5% bleach from last year that I put In straight away.

I then added baking soda to up the PH and when the chlorine started to fall, I grabbed three bags of the Clorox Xtra Blue that I had left over from last year, as I was out of liquid bleach. That’s when the staining appeared and I was convinced it might be a copper issue. I then got more liquid bleach and added three bottles. I’ve held off on putting in any more chemicals except for the Metal Magic yesterday.

In the past month, we’ve mostly had cool days (Upper in the 60s-70s) punctuated with some days of upper 80s and plenty of high humidity, rain and storms — typical St. Louis style.

The only other thing to take stab at here is that we’re probably overdue to change our sand filter media. We had the filter installed about 7 years ago but have never changed the media. However we have rarely had an issue with algae or anything else in that time. I’ve been very fortunate it’s been low maintenance to this point!