Black Stain! Help!

JamesW

TFP Expert
Mar 2, 2011
17,372
4 lbs of ascorbic acid should work.

Ascorbic acid doesn't always do well with copper. So, it might not work and it might even create more stains.

You're at risk for an algae outbreak due to the low fc. So, you want to complete the process as soon as possible or begin to use some chlorine or poly 60 algaecide.

If you get algae, it's going to be difficult to treat without causing copper stains.

Poly 60 should be available locally. Just look for the ingredients listed.

Sequestrant should be available locally. Don't get edta based sequestrant.

Take a picture of the cartridge before you clean it so we can see what it looks like. The colors can help identify the metals in the water. Turquoise is copper, brown is iron, silver is black or grey.

Be careful about raising the pH. What are all of the chemistry readings?
 
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bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
4 lbs of ascorbic acid should work.

Ascorbic acid doesn't always do well with copper. So, it might not work and it might even create more stains.

You're at risk for an algae outbreak due to the low fc. So, you want to complete the process as soon as possible or begin to use some chlorine or poly 60 algaecide.

If you get algae, it's going to be difficult to treat without causing copper stains.

Poly 60 should be available locally. Just look for the ingredients listed.

Sequestrant should be available locally. Don't get edta based sequestrant.
Thanks, just to verify, if I pick up all the ingredients, I can add them all in tonight, 1 hour apart, with pool pump running.
 

JamesW

TFP Expert
Mar 2, 2011
17,372
Thanks, just to verify, if I pick up all the ingredients, I can add them all in tonight, 1 hour apart, with pool pump running.
Correct.

If you want to use filter fiber, that can be helpful. Cleaning the cartridge can help a lot because metals get caught in the fabric and you can wash them out before they get back in the water.
 

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
So as an update, last night I put in
7:00pm: Fiber Cellulose in the skimmer: 2 bottles of Natural Chemistry Metal Free, around the edge of the pool and over the stain
8:00pm: ~36oz of Polyquat 60 around the edge of the pool., was using a solo cup to measure so not 100% precise
9:00pm: ~4lbs of asorbic acid,. Some in powder (around the whole pool) for and some in pill form (over the stain).

Below is a picture from this morning. The stains are almost completely gone, with only a few pretty light spots left.

Pool chemistry is:
PH: <7.0, it took 4 drops on the demand test to get it up to 7.1
FC: 0
CC: 0
TA: 40-50
CH: 70
CYA: I didn't retest, but previous test had it ~100. It may have come down a little since I stopped using the pucks the previous owner was using this last month.

I haven't had a chance to break down the filter and clean the cartridges yet. I will try to do that tonight. The pressure actually dropped from when I started last night (not sure that's a good thing).

I assume I'm moving from the stain removal phase to the getting the pool back in balance without an algae outbreak phase.

Please let me know what you think are the recommended next steps. I can run my Dolphin this morning to try to pick up more asorbic acid powder off the bottom, or let it sit on the bottom to see if the stains completely go away20190814_065437_resized_1 (1).jpg
 
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JamesW

TFP Expert
Mar 2, 2011
17,372
I would clean the filter and run the pump continuously for about a week.

Clean the filter again in a day or two.

Don't do anything to raise the pH directly. Increase the TA to about 60 or 70 and the pH will be fine.

Begin to add liquid chlorine until it begins to hold steady. The ascorbic acid neutralizes chlorine, so it's going to be tricky getting it to come back to a steady level.

Then, maintain the fc at 7.5% to 10% of the CYA.

Try to dilute the water with fresh water as much as possible to get rid of what's in the pool.
 

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
I would clean the filter and run the pump continuously for about a week.

Clean the filter again in a day or two.

Don't do anything to raise the pH directly. Increase the TA to about 60 or 70 and the pH will be fine.

Begin to add liquid chlorine until it begins to hold steady. The ascorbic acid neutralizes chlorine, so it's going to be tricky getting it to come back to a steady level.

Then, maintain the fc at 7.5% to 10% of the CYA.

Try to dilute the water with fresh water as much as possible to get rid of what's in the pool.
Thanks a lot. I have a slide, and a figure maybe I run that pump too, to bring up the ph a bit.

Should I be adding enough liquid chlorine to get up to that 7.5% range or do it now gradually, like 2ppm a day?

When will I know that the pool is safe to swim in. I assume the chlorine will need to be 7.5% of CYA and PH of 7.2. does that sound right?
 

JamesW

TFP Expert
Mar 2, 2011
17,372
Try to get the fc reestablished as soon as possible to prevent algae.

You're at a difficult time because too much chlorine can cause the metals to drop back out but too little can allow algae to grow.

Trying to recover from an algae outbreak without oxidizing the metals would be difficult.

Add it back as consistently as possible until it begins to hold.

For swimming, get the fc to hold at 7.5% of the cya, get the water clear and get the pH to at least 7.1.
 

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
As an update:

Last night I :
1. Cleaned the filter. See pictures of cartridges attached. I couldn't tell much from their color. They actually didn't look too dirty, and I couldn't tell anything from the color (I had cleaned them when I moved in about a week or two before this started). Based on the set-up I'm not sure a lot of solid sediment on the bottom makes its way into the filter.
2. Added 5lbs of baking soda (all I had)
3. Added more Cellulose Fiber
4. I kept the Dolphin z5 running all evening. It had some good runs that pulled a lot of the asorbic acid powder off the floor (still a ways to go), but some wasted time. Maybe for a different post, but I'm pretty frustrated with the Dophin,s performance in the new pool. It keeps getting stuck on the drains in the bottom. I didn't want to pay $70 each for unibridge main drain covers (I have 3 drains). I made weighted flower pots to cover them, but the Dolphin still gets stuck on them, although less than the naked main covers.
5. At about midnight I added 2 gallons of 12.5% liquid bleach, which I would expect to take it up to almost 5 from pool math.

This morning things looked good from a stain perspective, and I didn't see any algae. My readings were:
FC: 3.0
PH: 7.0
TA: 50

This morning I'll add more LC, and pick up more baking soda to add this evening. I feel good that I may be out of the woods, but please let me know if there are other issues I should be looking out for.


20190814_211422_resized.jpg
 

JamesW

TFP Expert
Mar 2, 2011
17,372
That looks pretty dirty. It looks more like silver than copper.

Since you added the ascorbic acid before removing the cartridge, the color of the cartridge won't be as useful because the metals in the fabric could have been removed by the ascorbic acid.

I would replace the cartridge.

I suspect that someone added silver algaecide in addition to copper.

In any case, it seems that you're getting things under control.

:goodjob:
 
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bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
That looks pretty dirty. It looks more like silver than copper.

Since you added the ascorbic acid before removing the cartridge, the color of the cartridge won't be as useful because the metals in the fabric could have been removed by the ascorbic acid.

I would replace the cartridge.

I suspect that someone added silver algaecide in addition to copper.

In any case, it seems that you're getting things under control.

:goodjob:
Thanks!

The cartridges don't look much different than these after a good hose down.

It is doing a good job of keeping the pool clear, but I will consider changing if they are putting me at risk of restaining
 

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
Just as an update, last night I checked Chlorine again and it had gone to 0 during the day, so I guess I'm not completely out of the woods. PH was at 7.0.

I added 5 more lbs of baking soda and 2 more gallons of LC. This morning I was at:

PH 7.2
FC: 3
CC: 0.5
TA: 60
CYA: 50-70 (I'm not great at this test, and was doing it at night inside vs. in the sun as directed).

I added another gallon of LC this morning. We'll see where we are this evening. We'd sure love to get in the pool tomorrow. It sounds like we just want our chlorine to hold before it's safe to go into.
 
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