Deep, stubborn stains in coping, need help

bkaiser

Active member
Aug 27, 2020
28
san antonio TX
We're in the process of restoring the decking and coping of our early 80's pool. The coping structurally is in good condition, however, there are deep black stains in most of the stones. Initially, we tried watered-down versions of 10% chlorine bleach and 20% muriatic acid, brushing each in and letting it sit for quite some time, then lightly pressure washing. That didn't do anything so we moved on to testing both just straight which also didn't do anything at all. All the chemicals were brand new and I'm out of ideas of anything I would have stronger at my disposal. is it possible that the stains are just too far embedded in these old stones?





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kimkats

Mod Squad
LifeTime Supporter
Jul 10, 2012
47,371
Tallahassee, FL
You did what I would have told you to. Well NOT the part about mixing the muriatic acid and chlorine.............that is asking for trouble as the fumes they form when put together are VERY toxic (saying this in case you did mix them as I can't tell for sure so want to put that out there so no one does think about doing it).

Okay so let see if we can think of something else to get that black out..............I do want to ask this............has the coping ever been "clean" aka with no dark areas?

Gel like bleach? I know they have it in "pens" to help you get it just where you want it. I am thinking it might stay better than the liquid.

Simple green is a suggestion my husband made. Just use care to not get it in the pool as I am not sure how it will impact the water balance. Soak a paper towel with it and let it sit on the stone making sure to get some down into the holes.
 

HermanTX

Gold Supporter
May 20, 2020
985
Katy TX
Pool Size
14600
Surface
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Chlorine
Liquid Chlorine
One idea is what I use to remove mold from shower grout. Soak a paper towel in standard bleach. Put on the area and leave the soaked filled paper towel on the spot for several hours (I leave mine in the shower overnight). Remove the paper towel and black is gone. Then just rinse to remove the bleach residue. FYI, if you just wash bleach across mold, it does not remove it, you have to let it soak for some length of time. If this doesn't work on your coping well you can use the same method for your shower as I know that works as I have done that successfully.
 
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bkaiser

Active member
Aug 27, 2020
28
san antonio TX
Just to clarify, I absolutely did not mix the two. I used them both straight in different areas to test. I did let the bleach sit for a few hours but not overnight. I can try that next.
 

HermanTX

Gold Supporter
May 20, 2020
985
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
Just to clarify, I absolutely did not mix the two. I used them both straight in different areas to test. I did let the bleach sit for a few hours but not overnight. I can try that next.
A important part is to keep the paper towel on it moist.
 

JamesW

TFP Expert
Mar 2, 2011
21,553
I suspect that the bricks were originally brown and turned white over time.

How old is the deck and coping?

How old is the pool?

There is no expansion joint, so I would expect that some of the bricks are becoming unbonded and loose.
 

JamesW

TFP Expert
Mar 2, 2011
21,553
How long have you been there?

If you just moved in, how do you know the history?

I suspect that if you cut into one of the bricks, you would find that the original color was brown.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,963
Evans, Georgia
If you can't make them look lighter (esp since apparently they were originally naturally dark) how about staining them darker so the coping stands out more?

Maddie :flower:
 

markayash

Gold Supporter
Mar 21, 2016
2,697
Atlanta Ga
Just a tip I heard form a " mold guy" he said mix dish soap with peroxide 50-50 and spray it on the mold. He said it will kill it..Van't remember the percent but stronger then normal drug store cheap stuff
 

JamesW

TFP Expert
Mar 2, 2011
21,553
I still think that the brown is the original color of the brick.

The white looks like some sort of coating on the brick.

I suspect that if you cut into a brick, it would be brown inside.

There is no expansion joint, which is going to put stress on the coping as the deck expands and contracts.

Is the deck and coping original?

Are the bricks still securely bonded or are they becoming unbounded from the top of the bond beam?
 

Candurin

Well-known member
Jun 30, 2017
96
Southern NJ
Just a tip I heard form a " mold guy" he said mix dish soap with peroxide 50-50 and spray it on the mold. He said it will kill it..Van't remember the percent but stronger then normal drug store cheap stuff
As a “mold guy” myself, this may work for a few surface colonies, you would have some difficulty with black mold (Chaetomium and other common geniuses) and therefore bleach would be better. The solution you mention is just for stains, really.

I am so glad I can use my fancy mycology and microbiology degrees on the pool forum! I’ve received so much help, felt good to give back, ever so briefly...
 
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