Unusual stains: Fiberglass pool

danobrien

Bronze Supporter
Jun 10, 2017
28
Cold Spring/NY
I know that stains have been discussed before, but I was still thinking it might be helpful to get some input. I just opened my fiberglass pool last week. Once the water began to clear I noticed discoloration and stains. There are streaks in the pool, that to me looks like the original color. I have attached a picture that show a V-shaped streak (scroll down to see the V) that I believe is the "cleaner" color. That means the rest of the pool is discolored. I did the puck test and there was no change. Also brushing does not seem to help. I've been slamming the pool for several days. It's not quite there yet since I am getting a combined chlorine of 1.5, but the water is relatively clear and the chlorine only dropped a couple of ppm overnight.

Here are my questions:
1. When I do the ascorbic acid test, do I need to get into the water or can I put the sock on the net somehow to hold it on the surface.
2. The pool has stones around it. Some of the cement between the stones was redone last year. This year when I opened the pool I noticed the cement that was used is cracked and in some cases was mushy. Some of it went into to pool. Could that be what has caused the discoloration?
3. Any other thoughts on possibilities:

1. CYA - is low at around 20; I know it needs to go higher but I don't think it is relevant to the staining. I've been adding trichlor tablets to increase it but may need to add CYA directly.
2. FC - been keeping around 12 or more
3. Alkalinity - was at 40 but increased now to 80
4. PH- About 7.5
5 CH- tested today at around 175.


Pool stains.jpg
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
21,896
San Dimas, CA (LA County)
Vitamin C test, I can help with. Mash a bunch up inside a sock or nylon, put a smooth clean river rock in, tie it to a string and lower it in. You can tie it to the depth you want and it will rest against the wall or floor.

That streaking looks to me like it might be Calcium scale. If you had stuff oozing down from mortar, you could have had localized super high pH and plenty of Calcium to form it without really throwing the rest of the chemistry out of whack.
 

danobrien

Bronze Supporter
Jun 10, 2017
28
Cold Spring/NY
I ordered the Jacks Magic Stain Id Test kit and had a positive reaction to the first and second packs. The first tests for "Iron, Cobalt and Spot etching" and the second for "Copper and scale stuff". Actually the second test was much more prominent. The stain does not look like Copper, so I guess it would be "scale stuff", which I assume means Calcium Scale. As I mentioned, my calcium level was low (around 100 or less), however, cement leaked into the pool. I was going to try the Jacks Magic to get rid of the scale (it's quite expensive-over $200 for my 20,000 gallon pool). One glitch is that they say the TDS must be 1200 or below. I went to a pool store and they told me my TDS was 1300. Not sure why Jacks Magic cares about TDS when according to this site TDS is not important. All my other number are in range:
Free Chlorine : around 3.5 ppm
CC Chlorine: .5
PH: 7.3
Alkalinity: 80
Cyanuric acid: 20
Calcium Hardness: 175

The copper and scale test was very effective on the stain, but I am reluctant to use it, since they are saying my TDS must be below 1200. However, it's not easy to test for TDS. Not sure if the pool store did an accurate reading, and not sure why Jacks Magic insists on TDS below 1200.

Also regarding whether it is calcium scale, I don't feel anything rough on the surface.

dan
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I would also be hesitant to invest $200 in those products. If it is indeed calcium related, your CSI level of the water appears to be in the negative rigth now anyways. You can confirm using PoolMath and entering your water temp. You might try leaving it slightly negative (i.e. -0.1 to -0.3) for a couple weeks and continue consistent brushing to see if it helps. I didn't realize those "packs" combined different possibilities, so that can be confusing. For sure though, it crushed Vitamin C tabs remove a spot, it's iron. If it gets worse with C-tabs or chlorine, it would be copper. In that case, dry acid should help. So if none of those apply, it may indeed be related to that plaster fiasco.
 

danobrien

Bronze Supporter
Jun 10, 2017
28
Cold Spring/NY
I would also be hesitant to invest $200 in those products. If it is indeed calcium related, your CSI level of the water appears to be in the negative rigth now anyways. You can confirm using PoolMath and entering your water temp. You might try leaving it slightly negative (i.e. -0.1 to -0.3) for a couple weeks and continue consistent brushing to see if it helps. I didn't realize those "packs" combined different possibilities, so that can be confusing. For sure though, it crushed Vitamin C tabs remove a spot, it's iron. If it gets worse with C-tabs or chlorine, it would be copper. In that case, dry acid should help. So if none of those apply, it may indeed be related to that plaster fiasco.
When I first noticed the stain after the opening, my calcium level was less than 100. It was low for several weeks and brushing did not help much. But that second Jacks Magic test was very prominent. It eliminated the staining completely. If it is calcium staining would it also feel rough? Also I am wondering why the instructions for Jacks Magic say the TDS should be below 1200 in addition to the other measurements (chlorine, etc..)
 

danobrien

Bronze Supporter
Jun 10, 2017
28
Cold Spring/NY
Wow, Jack's Magic did the trick. Worked amazingly well. I used stain treatment #2 - The blue stuff followed by the copper and scale stuff. I saw the stains clearing up almost immediately. After 24 hours they appear to be gone altogether. It resolved the significant staining that appeared after the spring opening, but also seems to have taken care of stains that have been there longer term. I really like the stain id test kit. There was a very positive reaction to the second test, and the stain treatment number 2 worked quite well. Well worth the price!
 
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danobrien

Bronze Supporter
Jun 10, 2017
28
Cold Spring/NY
Did you lower your TDS? If so, how did you do it? I have something similar going on with my Fiberglass pool.
First get the stain id test kit to determine which treatment to use. I made sure all the parameters as per the instructions are in balance (Chlorine, Alkalinity, PH, Cyanuric Acid, and Calcium Hardness). They mention TDS but I did not measure that prior to using the stain ID test kit. I assumed based on my readings on this site that if those other parameters are OK then the TDS will be OK as well. After a positive test from stain id test kit #2, I did take a sample to the pool store to measure my TDS. I got a reading of 1300 (my chlorine was around 5 at the time, so that may have been the reason the TDS was a bit high.) The instructions say the TDS should be 1200 or below, but I called Jacks Magic and was told by the technician that 1300 is OK.

Have you measured your TDS? If so how did you measure it and what are your numbers? Also is everything else in balance? The stain id test kit was around $15.
 

mknauss

Mod Squad
TFP Expert
May 3, 2014
18,204
Laughlin, NV
You all realize the bulk of your 'TDS' is salt?
TDS is meaningless, the components are what matter. Primarily CH and CYA. Salt if you have a SWCG.
 

CarolineM

Silver Supporter
Jun 20, 2018
117
Annapolis, MD
Thank you for your response.

All of my numbers are good, water is perfectly clear as seen in my picture from today. I have not had my TDS measured, I will have to go to the pool store for that. I am going to order the Jacks test kit and go from there. Everything below the water line has a whitish hue to it, it is perfectly smooth. I have tried scrubbing it off, magic eraser, even scraping with my nail and nothing comes off.
 

calinb

Well-known member
Jul 18, 2018
70
N. Central, ID
Though it's not covered in the Jack's Magic Stain Identification Kit or The Copper and Scale Stuff instructions, Jack recommends using The Purple Stuff instead of The Blue Stuff for high TDS (or salt pool) stain removal. Scroll down to the flow chart here:

Our Program | Jacks Magic

The instructions, including the substitution of Purple for Blue Stuff, is also covered on the Pool Geek store Copper and Scale Stuff page.

Last year I did a ProTeam Metal Magic "sponge test" and used MM to remove my dark gray stains, but it left my lighter color tan stains. Just today I used the Jack's ID kit and the Copper and Scale Stuff was the clear winner with the remaining stains. Ascorbic acid doesn't do anything to them, except perhaps darken them.

Now I'm debating whether to spend the $200 for the Jack's program. Perhaps even more disconcerting is the Pool Geek admonition to not swim in the pool during treatment, but nowhere is a treatment period exactly specified, other than than to say stain removal may take several weeks!

I found some copper trichlor pucks the previous owner had left behind so copper stains make sense. The stains removed by MM were iron stains from our spring fill water (and my CuLator did, in fact, turn yellow-brown).
 

danobrien

Bronze Supporter
Jun 10, 2017
28
Cold Spring/NY
Though it's not covered in the Jack's Magic Stain Identification Kit or The Copper and Scale Stuff instructions, Jack recommends using The Purple Stuff instead of The Blue Stuff for high TDS (or salt pool) stain removal. Scroll down to the flow chart here:

Our Program | Jacks Magic

The instructions, including the substitution of Purple for Blue Stuff, is also covered on the Pool Geek store Copper and Scale Stuff page.

Last year I did a ProTeam Metal Magic "sponge test" and used MM to remove my dark gray stains, but it left my lighter color tan stains. Just today I used the Jack's ID kit and the Copper and Scale Stuff was the clear winner with the remaining stains. Ascorbic acid doesn't do anything to them, except perhaps darken them.

Now I'm debating whether to spend the $200 for the Jack's program. Perhaps even more disconcerting is the Pool Geek admonition to not swim in the pool during treatment, but nowhere is a treatment period exactly specified, other than than to say stain removal may take several weeks!

I found some copper trichlor pucks the previous owner had left behind so copper stains make sense. The stains removed by MM were iron stains from our spring fill water (and my CuLator did, in fact, turn yellow-brown).
I used the copper and scale stuff because the stain id test kit was very positive for that, but my stains were most likely not copper, but rather scale. Also my stains were relatively new, but also quite extensive and significant. The copper and scale stuff worked immediately. In a day most of the stains were gone. I stopped the treatment in 2 days. You are correct that the instructions say the removal may take a couple of weeks. To stop the treatment you have to add baking soda to bring up the alkalinity and the PH. That can take an additional 2-3 days since there is a limit to the amount of baking soda to add per day.

I guess every case is different. I believe the reason you cannot swim is due to the very low PH during treatment. Mine went down to 3.4. The technician at Jacks Magic is very helpful if you have any questions.
 

calinb

Well-known member
Jul 18, 2018
70
N. Central, ID
I used the copper and scale stuff because the stain id test kit was very positive for that, but my stains were most likely not copper, but rather scale.
<snip>
Thanks for the information! I'm contemplating the Jack's Copper and Scale Stuff treatment myself. I'm glad it worked for you and it worked quickly.

I removed what were surely iron stains in our pool (from spring water fills) late last season using the maximum dose of Metal Magic but it didn't touch the copper stains (as subsequently diagnosed with the Jack's test kit). They are no doubt from the copper laced trichlor pucks the previous pool owner used, because a local lab tested our spring water at 4.4 ppm Iron but essentially zero copper.

Ascorbic acid testing on the remaining stains sometimes results in a slight darkening/graying of the stains. While citric acid lightens the stains, the effect is slight and it take a long time (even after using it on areas pre-treated with the remaining Jack's kit O2 shock, which didn't help make the Jack's Copper and Scale Stuff more effective either). I think the Metal Magic treatment already pulled the scale out of the pool.

So I'm thinking about doing the Jack's Copper and Scale Stuff program for these old copper stains, but I've also found usage testimonies here on TFP of month-plus long battles with it on stains similar to mine. Though the Jack's test lightened my stains, it didn't completely remove them. It just lightens them more than citric acid. I'm not sure I'm up for taking the pool out of service and waging another prolonged war on these entrenched stains! The pool is probably close to 30 years old and it might be best to wait until it needs an overhaul and full refurbishment with re-plastering, if ever.

On the other hand, I could try a citric acid treatment regardless. It's far cheaper than the Jack's treatment and seems to be less drastic in terms of post-treatment water balance recovery, which mostly requires a lot of bleach from what I've read on TFP. I probably have too much bleach in inventory this year anyway! ;)
 
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