This spring I will finally conquer this stain

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
Since getting the house, I have had a large stain in the bottom of my gunite pool. It is large and kind of cloud shaped and dark brown. The stain has not changed size or color over the years except where I have attempted to treat said stain. Previous owners did not do a good job of maintaining the pool and seemed to never manage the PH levels. I found old chemicals in the shed when we moved in including algeacide and PHOSfree like they used them frequently.

I did pool school as soon as we got the house, and I follow it closely. The pictures you see are from my pool as it is coming down from a SLAM. I live in Texas and the power outage browk some plumbing (and my heater) so the pool was down for about a month. When I took the cover off, it was a mess with leaves and algae. I have cleared all of that up but the stains still persist. I am hopeful the community can help me solve this one as it is a head scratcher.

Pool details:
15K pool and hot tub (with Pentair heater)
Water source is city water
SWG Normal operations is 3400
Normal operating levels:
FC: 2.5 to 3.5
CC: 0
CYA: 50
PH: rises daily in normal operations. Starts the week at 7.4 and by the end of the week it is close to an 8 depending on weather and I knock it back down with acid

Current:
Salt: 2100 (not adding salt until I figure out the stain stuff)
FC: 11 (coming down as the SLAM is over)
CC: 0
CYA: 20 before I started slam (plan to add more once stain stuff is over)
PH: Haven't measured since starting the SLAM, was 7.2 before beginning (added acid before starting SLAM)

Ok so what about this stain? Here is what I have tried:
First time I SLAMMED the pool (slight streaks showed up in the stain like it was doing something, but could not expand/grow it)
Asorbic acid tab rubbed on stain: no change
Asorbic acid tab crushed and applied to stain: slight color lightening but clearly did not remove stain
Chlorine tab rubbed on stain: no change
Chlorine tab left sit on stain for 12-14 hours: obvious reduction in stain (round circle of clean)
crushed chlorine tab left sit on stain for 24 hours: Stain reduction
Wire brush: no change
Wire brush with 30PPM of FC: no change
Acid applied via submersable applicator with a cup of acid on it: works if left on spot for 20+ minutes less than that no change
calcium hypochlorite powder in a sock over night on stain: no change
Pouring calcium hypochlorite powder over the stained area: disolves before reaching bottom, no change in stain

You can see in the photos where my testing has improved the stain, but now it almost looks worse than if I wouldn't have done anything. You can see the circles where I have had sucess with the tabs and the acid in a dispenser. You can see the streaks where the initial SLAM and application of crushed chlorine tabs worked. Also, I have done this testing over last season and even after the rough start to this season, the stain removals have held. So whatever it is, is not growing or changing.

Anyone have any ideas of what to try next? Here are the things I am thinking of trying:
Jack's Magic stain remover (the Blue Stuff) (Perhaps the stain is manganese?)
Acid wash without draining (never done this before)
Crazy chlorine levels (Highest I have ever gone is in the 30's, so higher than that)

Any help would be super appreciated as this is frustrating me to no end. Thanks.
 

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Last edited:

Cwiggs

Well-known member
Aug 31, 2019
141
Phoenix, AZ
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
Sounds like you read the blog post about this here: Stains in Your Pool - Trouble Free Pool If not, give it a read.

Have you tried using ascorbic acid (Vit C) yet?

Have you verified if there are metals like copper in your pool yet?
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
Sounds like you read the blog post about this here: Stains in Your Pool - Trouble Free Pool If not, give it a read.

Have you tried using ascorbic acid (Vit C) yet?

Have you verified if there are metals like copper in your pool yet?
I haven't done a metal test yet. I can do that, but I was thrown off by the effect that Chlorine has had on the stains and the fact that they don't come back.

I have tried asorbic acid (I mislabeled it in the post and fixed it now). The tabs rubbed on it had no effect. A bunch of ground up tablets placed on it and left over night did make it a bit lighter but still there.

The most effective methods so far are: leaving a chlorine tab on it and using the acid dispenser thing (but boy are they slow) and with such a large stain, it is not really possible to do the whole thing.
 

Cwiggs

Well-known member
Aug 31, 2019
141
Phoenix, AZ
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
Sounds like your stains might be a combination of copper and organic stains?

You mentioned you already slammed the pool did you follow the advice for organic stains in the "stains in your pool" link? It says:
To remove organic stains raise the FC up between 60% and 100% of shock level for your CYA, Chlorine / CYA Chart, and brush often, daily if you can.
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
Sounds like your stains might be a combination of copper and organic stains?

You mentioned you already slammed the pool did you follow the advice for organic stains in the "stains in your pool" link? It says:
Yes, Living in Texas, I run my pool year round to maintain it. However, the power outage caused some pipes to break and I was stuck for a month waiting for parts. During that time, my pool got really bad for me with Algae growth and leaves in the bottom of the pool. To get it back up, I vaccuumed out as much debri as I could see and then ran the pump with 18 - 20 ppm of Chlorine for the first day, brushing it every 2 - 3 hours and then cleaned the filters after 32 hours. After that, the pool looked clean but the water was a bit cloudy and the CC was at 1. So I held the pool at 15 ppm of FC for 24 hours and then did an overnight chlorine test and confirmed no overnight loss and no presence of CC. That concluded yesterday.

Both the initial level of chlorine and the 15ppm I held it at are above the CYA chart for a SLAM.

I have heard that perhaps holding it at a crazy high amount would help. But I am nervous about going that high in Chlorine. Is there a risk there?
 

Cwiggs

Well-known member
Aug 31, 2019
141
Phoenix, AZ
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
Did you see any change in the stain after your slam process?

I have heard that perhaps holding it at a crazy high amount would help. But I am nervous about going that high in Chlorine. Is there a risk there?
No risk that I'm aware of other than you can't swim in the pool and measuring other chemicals (like pH) is difficult or impossible while FC is high.
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
Did you see any change in the stain after your slam process?


No risk that I'm aware of other than you can't swim in the pool and measuring other chemicals (like pH) is difficult or impossible while FC is high.
I have 7 gallons of bleach and one bag of powder. I could just go crazy and dump it all in tonight and see what it looks like in the morning. Also, since chlorine settles to the bottom, I suppose I could run the pump for 30 minutes and then turn it off so hopefully it settles to the stain overnight. Then get up and brush it in the morning before turning the pump back on?

I can't say about pre-slam, I couldn't see the bottom of the pool then. But the stains look in line with what was there before it got bad. I know a chlorine tab will make a clean circle if I leave it there long enough though. I also know, it doesn't come back to the circle. (I have a couple that are 2 years old at this point)
 
Last edited:

Cwiggs

Well-known member
Aug 31, 2019
141
Phoenix, AZ
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
When you say you have a bag of powder I assume that's dichlor? dichlor and trichlor will introduce CYA, so be careful not to raise the CYA too high. Plus if you increase the CYA your FC for SLAM will be higher. I also wouldn't let the powder sit on the plaster; it might be fine, but I wouldn't want to damage anything.

If the stain comes off with a trichlor tablet then I would follow the blog post about stains. You can raise your FC to 60% of the SLAM level, and brush the stain. If the stain doesn't come off raise it to 100% of slam and keep brushing. Hopefully you'll see a change in the stain.
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
When you say you have a bag of powder I assume that's dichlor? dichlor and trichlor will introduce CYA, so be careful not to raise the CYA too high. Plus if you increase the CYA your FC for SLAM will be higher. I also wouldn't let the powder sit on the plaster; it might be fine, but I wouldn't want to damage anything.

If the stain comes off with a trichlor tablet then I would follow the blog post about stains. You can raise your FC to 60% of the SLAM level, and brush the stain. If the stain doesn't come off raise it to 100% of slam and keep brushing. Hopefully you'll see a change in the stain.
Well I just poured in all the bleach I had left. It should put me at close to 50ppm on Chlorine. I am going to run the pump for a half hour to stir and then shut it down, check the FC, and brush it. I will brush it every couple hours until bed. Then let it settle over night and then in the morning brush again before turning the pump back on. If this improves the staining, I will buy more in the morning and keep it up until the stain is gone. If it doesn't, I will explore treating it as a metal stain.
 

Cwiggs

Well-known member
Aug 31, 2019
141
Phoenix, AZ
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
50ppm is way, way higher than you need, I would follow the guide otherwise you might just be wasting money on chlorine. The chart here says with your CYA at 20 your slam is 10ppm of FC, if your CYA is 30 it's at 12ppm FC.

hopefully that works out though, keep us updated.
 

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heyyou488

Member
May 25, 2020
22
Pflugerville, TX
50ppm is way, way higher than you need, I would follow the guide otherwise you might just be wasting money on chlorine. The chart here says with your CYA at 20 your slam is 10ppm of FC, if your CYA is 30 it's at 12ppm FC.

hopefully that works out though, keep us updated.
Will do. I have been over 10 ppm for 4 days and haven't seen a change. I am hoping that pushing it this much higher and adding a lot of brushing will result in goodness. If it doesn't, I am out less than $40 (Walmart bleach was on sale) and on the plus side, I didn't have to go wait in the return line. HA
 
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sktn77a

Gold Supporter
May 16, 2010
2,028
Chapel Hill, NC
Sounds like your stain is pretty much all organic (dirt, leaves, etc). Local application of chlorine would appear to be the best bet. Dichlor or trichlor granules in a sock and moved patiently all over the stain area should get rid of it.
 

JamesW

TFP Expert
Mar 2, 2011
24,197
It looks like copper to me.

Probably the only things that might remove it would be a zero alkalinity treatment or sulfamic acid.

Zero alkalinity and sulfamic acid will attack metal. So, you would need to protect any metal in the pool or system.

If it works, you will have to drain to get rid of everything so that it doesn’t come back.

Draining can float the pool if the ground water is high.

Do at your own risk.

Consult a local qualified professional before deciding what to do.
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
Will do. I have been over 10 ppm for 4 days and haven't seen a change. I am hoping that pushing it this much higher and adding a lot of brushing will result in goodness. If it doesn't, I am out less than $40 (Walmart bleach was on sale) and on the plus side, I didn't have to go wait in the return line. HA
Ended up with enough bleach to reach 41 ppm. While higher than I need to SLAM, I brushed it 4 times last night and once this morning and still looks the same. It doesn't even look lighter. It is supposed to be cloudy today so I would expect the chlorine levels to remain high for a while. I will brush it 3 or 4 more times today to see if it makes any change. Like I said, this test was simple since I had the bleach and honestly returns to Walmart annoy the **** out of me because there is always a long line, so no loss there.

Going to pick up the Jack's Magic Stain ID kit at the pool store today and use it once the chlorine levels get below 10 ppm.
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
It looks like copper to me.

Probably the only things that might remove it would be a zero alkalinity treatment or sulfamic acid.

Zero alkalinity and sulfamic acid will attack metal. So, you would need to protect any metal in the pool or system.

If it works, you will have to drain to get rid of everything so that it doesn’t come back.

Draining can float the pool if the ground water is high.

Do at your own risk.

Consult a local qualified professional before deciding what to do.
Yeah, I am not draining my pool this season. Let's see if we can get there on the Jack's Magic. I have run a metal test on the water a couple years ago and there was no real metal in the water. If I had to guess, the previous owners were using some Phosphate remover that they shouldn't have, or got fertilizer in the pool.

The two pool folks I talked to in the area one thought organic and the other thought maganese. I feel like all the slam level chlorine and brushing I have done in a week has eliminated the organic.
 

JamesW

TFP Expert
Mar 2, 2011
24,197
In my opinion, it's copper regardless of what a metal test shows.

If all of the copper is embedded in the plaster, there won't be much in the water.

You can have bad metal stains with no detectable metal in the water.

In my opinion, a zero alkalinity or sulfamic acid treatment are the most likely to do anything worthwhile.

You don't necessarily have to drain and refill after the process.

If you use sulfamic acid, it will convert all of the fc into cc for months.

Both treatments are aggressive to metal. So you have to take precautions to protect any metal in the pool or system.

Copper heat exchangers are susceptible to damage from either treatment.
 

JamesW

TFP Expert
Mar 2, 2011
24,197
I think that there is also probably silver, iron and some scale.

Copper can come from algaecide, ionizers, heaters etc.

Silver can come from algaecide or ionizers.
 

JamesW

TFP Expert
Mar 2, 2011
24,197
Can you show a picture of the equipment?

Was there ever an ionizer installed on the system?
 

heyyou488

Member
May 25, 2020
22
Pflugerville, TX
In my opinion, it's copper regardless of what a metal test shows.

If all of the copper is embedded in the plaster, there won't be much in the water.

You can have bad metal stains with no detectable metal in the water.

In my opinion, a zero alkalinity or sulfamic acid treatment are the most likely to do anything worthwhile.

You don't necessarily have to drain and refill after the process.

If you use sulfamic acid, it will convert all of the fc into cc for months.

Both treatments are aggressive to metal. So you have to take precautions to protect any metal in the pool or system.

Copper heat exchangers are susceptible to damage from either treatment.
Well lucky for me, my heater froze during the Texas government imposed power outage. As such, it is by-passed all together since the parts are unlikely to become available and I have not replaced it. Given this, the metal that I can think of is:
1) Salt cell
2) Pool light
3) Hot tub light
4) The screws holding the drain covers on

I could probably cover the lights with petrolium jelly or something before I begin. If I am going to do it, I would likely do the muriatic acid route. Frojm reading here, it sounds like 4 gallons of Muriatic Acid for a 15K pool would likely be enough to get there. Do I brush it while it is there? (I have an aluminum pool and nylon bristled brush)

My concern here is that it does desolve the finish some. Would you think Jack's Magic Stain remover is even worth a shot first to avoid the finish issue? Or just do it and get a pretty pool from it.
 

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