Spreading grey spots

[Bbody]

Our pool is eight years old. About a year or so after construction, we started seeing a greyish spot on the bottom that slowly started spreading I have posted a picture of what it looks like now. I have read about "mottling" and the causes, but it looks and sounds like issues with concrete and troweling would have started showing soon after it was filled - not a year or two later. I do know that my husband did have issues with chemical balancing a couple of years ago and it seemed to get worse then - but it has continued to "grow" over the last couple of years . The pool chemicals are in check now - although we do have some black spots after winter which we are following directions to remove them - wire brush, brush X2/day and super chlorinate, etc.
So, I guess we are trying to determine what the cause of the mottling is and if it can be removed or treated? Or, is it going to require refinishing.

12000gal
in-ground pool with spa and spillover
SWG
Florida
screened enclosure

 

[JamesW]

Looks like it’s probably copper staining. Copper stains are usually turquoise or black/gray depending on the oxidation state of the copper and the copper compound that is causing the stain. The turquoise staining is pretty even and harder to notice due to lack of distinct contrast.

Typically, calcium hypochlorite, if allowed to settle, will further oxidize the copper and change it from turquoise to black. Your staining looks like where chemicals would settle.

Most likely, at least some of the copper has come from the heat exchanger in the pool heater.

Superchlorinating will only make the stains worse.

 

[pooldv]

Welcome to TFP!

You can add your pool info to your signature as shown here, Pool School - Read This Before You Post

This article might be helpful in diagnosing your issue, Diagnosing Pool Plaster Problems

To determine if it is a stain and what the stain is you can order this kit, Jacks Magic Stain Identification Kit JMSTAINID at Sunplay

If you use algaecide many of those add copper as do most "mineral" systems. If your heater has a copper heat exchanger and your PH spent some time below 7.0 that could be the source of copper.

 

[Bbody]

Should I continue to balance before stain ID testing

Merged by moderator. Please keep all your related questions together. Thanks, jblizzle

I had posted about the spreading grey staining on the pool bottom - thanks for the replies. I am determined to get this pool back in shape - I think it has been neglected too long by having others test and treat (or not). For example, Husband took a sample of the pool water to the pool "experts" yesterday (this is what we have been doing the last few years)-- they told him that the chlorine was "0" and sold him chlorine. Said everything else was still "fine". I thought that was weird as we have a SWG that has been set on 80% and clear water. I opted NOT to put in the chlorine. I had already ordered the Taylor 2006 test kit and the Jacks Magic Stain ID (per your suggestion). I received the kit today and tested the chlorine as well as the other chems.

FC - 8.0 (I turned the generator down to 40% and will test tomorrow) -- hmmm --seems strange that the chlorine would jump up like that- I even tested with a strip just to confirm.
CC - 0.0
PH 8 (acid demand - +4 -- so added 2 quarts MA and will test tomorrow)
Total Alk - 150
Cal - 220
CYA - 35ppm

Needless to say - I am going to continue to do my own testing from now on.

After reading "tons" of post and articles - I really am thinking that these ugly grey stains are from copper. Not sure if it is from the heater, though, because I know that the PH as never gotten really low before. Whenever we had it tested over the last few years, we have always had high PH and have to bring it down. But, we have put in a lot of algaecide over the last few years as we have had issues with black algae. Little black spots scattered or sprinkled all over. So - my questions:

1. Should I continue to work on getting the chlorine and ph in line before using the Stain ID kit?
2. I don't want to use algaecide to get rid of the black spots - If I get a SS brush and use every day with the appropriate chlorine level, will that work?
3. We have a "Super Chlorinating" cycle on the SWG - should I bump that up to deal with the black algae - along with brushing. Or, will this cause the grey shading (if it is copper) to worsen?


Thank you,

 

[frustratedpoolmom]

Hi there...
1. Yes - and increasing your CYA level to at least 60 will help as well. Are you familiar with why a higher CYA level is recommended for an SWG?
2. Yes
3. Not necessary and using liquid to bump is always better. Super Chlorinate doesn't always raise the chlorine up high enough, fast enough, and can shorten the useful life of the cell. Do you have any pictures of the "black algae" you were dealing with...

What kind of algaecide were you using?

 

[Bbody]

Thanks for the response.
1. I know I should increase it to at least 60, preferably a little more with a SWG - but not sure why - other than improved performance
2. Great - brushed it just now with the new SS brush -
3. below are the pics of the black algae. I just checked the last bottle we used - sun Coast Super Black Algaecide with Copper complex mix at 9.5% (ugh)
Today's test results
FC - 6
CC - 0.5
PH 7.9 ( acid demand at +2 - I added 1 quart MA)
Total Alk - 120
CH 230 ( the article said that I should raise this to 350 - ???)
CYA - 35 ( I plan to get more stabilizer tomorrow and put that in )

 

[frustratedpoolmom]

Before you add the stabilizer... I need a bit more info...

Do you have current Black Algae spots? Were you able to eliminate them previously with what you were doing?

Have you read the article in pool school about water balance for SWG and why it's recommended? There are several reasons why this is a good thing

You have to decide if you want to try to remove the copper stains (extremely tedious and difficult) or do you think you can learn to live with them, or even accept them as a badge of honor of being pool stored and never will be "had" again?

Hold off on the CH adjustment for now, one thing at a time... (but 250-300 is more than sufficient...)

 

[pooldv]

As FPM says you can try to get rid of the stains, drain (or partial drains) your pool to get rid of the copper and refill. Or it is perfectly fine to have the stains and have a good summer

 

[Bbody]

I had read the article on water balance with a swg, the article said CH at 350. I want to get rid of the staining - it currently covers about half of the bottom and is very ugly. I will probably do the stain ID testing tomorrow, but I am becoming more convinced that it is copper staining.
In the past - the algaecide worked on the black spots when they spreaded - but if we caught it early in the season, then a good shock worked.

 

[JamesW]

Jack’s has a copper remover. However, I would recommend reading the following posts before considering using it.

CC of 50

Rebalancing after Jack's Magic #2 - Page 2

I don’t know if the Jack’s number 2 would help. I think that the stains are bad enough that only an acid wash would help. Even then, the plaster would be seriously etched and rough and all of the stains might still not come out.

STAIN SOLUTION #2 - The Copper & Scale Stuff - 5 lbs - #JMCOPPER05 - Stuff for the Pool - Our Stuff - Product Catalog - Jack's Magic Products, Inc.

http://www.jacksmagic.com/pdfs/FAQ-Stain2-Treatment.pdf

 

[Bbody]

Thanks James and FPM - I truly appreciate the discussion and help.
I am still undecided how to proceed with the stain removal (or if I will at all) - until I definitively identify it. Now that the PH is getting more inline (although TA is still) high, it seems that the grey shading is "maybe" lighter than before. Hard to say. But I have been brushing those little black spots with the SS brush and some have actually disappeared.
Todays readings
FC 6
CC - 0.5
PH 7.4
TA - 110 (still)
CH - 230
CY - 35 (was wanting to hold off on adding more until after I used the stain ID kit.

I have had to put water in the pool today and decided to test the PH and TA in the deep well water source - FC - 0, PH - was undetectable so must have been below 7.0 - but the TA was 160+ (I didn't want to waste my test reagents so I stopped at that point) Is this going to make it more difficult to bring down my TA - or will it balance out since the PH in fill water is way low?

 

[Bbody]

Now, I feel I am back at square one. I performed the Jack's Magic stain ID kit and it was inconclusive! The packet #1 and #2 had no significant difference - I continue on through the rest and found that the last one - #1 and then #2 had a very slight change - but not enough to say for sure -- might have been wishful thinking on my part. Now that the PH and other items are in line, the water is crystal clear and I can see that the color variations on the bottom run from whitish "scale" appearance, to varying shades of grey and then more of a brownish tint towards the edges. Could this be organic?. Even though we have a screen enclosure. I am just at a loss right now as to what it is and how to get rid of it. I am beginning to think that maybe we will just live with it for now.

 

[JamesW]

I am 99% sure that it’s copper stains. You might also have black algae, which complicates things. An acid wash might get you back to a clean plaster, but the surface would end up very rough. Probably best to leave it or replaster.

 

[Bbody]

I agree - even with the test fail - it looks like copper. I think we are going to just live with it and then consider a no drain acid wash late fall. We'll see. Black algae is almost gone. I keep brushing every day. Fc is 6 today. Thanks for the info!!

 

[pwomack]

Did you ever find a solution to this problem? I am dealing with something very similar.