Black stains just keep getting worse

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
FC 6
CC 0
PH 7.8
TA 90
CH 400
Cya 80ish

Salt pool
Pump runs 8am-10am @3200rpm
10am - 8pm @ 1700rpm
8pm - 10pm @ 3000rpm

Standard pentair cartridge filter

Maintenance schedule
Wash filter once monthly
Check water twice monthly and adjust

All that said, these stains are getting worse. A stainless brush doesn’t even touch them

Pool store gave me some granules you sprinkle on them and let it sit overnight with the pump off and it went away but a couple weeks later it came back. When I wash the filter it seems like there is green slime stuff on it (assuming algae) but it’s weird cause my numbers are right

Is slam the right approach at this point?
 

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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Your numbers above (missing the TA) aren't bad at all if they are maintained that way year-long. WPB (West Palm Beach) I'm assuming? No chance of well water or iron in the local supply? Any chance you've used pool store products that have copper in them like "some BLUE" or algacides? The stains could be copper. Or if the algae has been in the water long enough, embedded in the plaster.

Try the following:
Vitamin C tablets lift the stain - iron
Dry acid lifts the stain - copper
Chlorine Tab rubbed on the stain for about 5 min - algae.

Your comment "Check water twice monthly and adjust" .... too long between tests. That's okay for CYA and CH, but your FC should be tested everyday, and pH about every couple days. TA perhaps weekly if no major water changes. So I'd watch those a bit closer to see if there are any odd patterns. Let us know how the stain testing goes.
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Your numbers above (missing the TA) aren't bad at all if they are maintained that way year-long. WPB (West Palm Beach) I'm assuming? No chance of well water or iron in the local supply? Any chance you've used pool store products that have copper in them like "some BLUE" or algacides? The stains could be copper. Or if the algae has been in the water long enough, embedded in the plaster.

Try the following:
Vitamin C tablets lift the stain - iron
Dry acid lifts the stain - copper
Chlorine Tab rubbed on the stain for about 5 min - algae.

Your comment "Check water twice monthly and adjust" .... too long between tests. That's okay for CYA and CH, but your FC should be tested everyday, and pH about every couple days. TA perhaps weekly if no major water changes. So I'd watch those a bit closer to see if there are any odd patterns. Let us know how the stain testing goes.


Yes, west palm beach. I forgot TA but I added it

Couple pieces of information I think I should share

For the first year and a half of pool ownership my SWG was set at 65 and slowly but surely I had to keep lowering it because the FC was over 8...I’m down to 25 now and my FC is apparently stil too high.

I do fill the pool with well water (through my water system) but I have to do that very rarely and I can’t correlate a fill to the current issues... we get so much rain that I drain my pool way more often than I fill it.

FWIW I tried a chlorine tablet and it didn’t touch the stain... but the granules the pool store gave me knocked em right out... seems like pure chlorine or something but they came right back.

When I go under water and scratch and pull at it nothing comes up... but it’s spreading for sure and it’s only on the areas my vacuum doesn’t get.
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,851
SW Indiana
Oh, my local pool store owners are on a Facebook group for my area and they are saying phosphates are the issue.
Nope. Black stain is likely copper. The tablets or chlorine granules would have the same effect.

Pool stores like to claim phosphates cause every problem and phosphate remover will cure all of them. Just a money grab the way they promote it.
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
So I did a bunch of maintenance this morning... here are the results

FC8.2
CC 0.2
PH 8
TA 90
CH 400
CYA 40ish

How can my FC be so high with my SWG @ 25?

I also cleaned the SWG, although it wasn’t that dirty. In the pics you can see the green slime on top of the filter and one where I half washed it off.

FWIW I added a quart of acid to bring the PH and TA down
 

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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Based on the pics, additional info, and earlier history you provided, I'm inclined to believe you have an algae issue that perhaps has gone-on long enough to where it is embedding in the plaster/steps - possibly even black algae. That's why some of it faded when you let the granules sit overnight. The cart filter, other than the green slime you noted, appears to not have any orange, brown, or green staining indicative of copper or iron. I did not see however any updates on trying the Vitamin C tabs or dry acid on the staining. Since you do fill from a well, there is the potential for iron levels to build unless you are exchanging water fairly often.

Regardless, green slime is never good and an indication you need to perform a SLAM Process to remove the algae. Follow that SLAM page carefully for best success. You have a good test kit, so once the SLAM is passed and completed, you'll want to test the FC and pH more frequently. Once the SLAM is completed, continue to evaluate the stains for changes. If they are embedded organic, the elevated FC SLAM level should over time help to lessen them (with brushing). If they are from iron, the Vitamin c tabs will confirm. Not saying the stains are from iron, but also remember that when iron levels increase in a pool, two things tend to irritate that iron to make it precipitate out - a high FC and/or high pH. Another reason to test those two fairly often each week. Let us know how the testing and/or SLAM goes.
 

JamesW

TFP Expert
Mar 2, 2011
20,329
I don't see copper on the cartridge. So, it might not be copper causing the stains, but it's not conclusive.
 

setsailsoon

Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
3,336
Stuart/FL
Rich,

FC isn't only dependent on your production %. Sounds like your just not consuming that much. Pretty common with colder water temps this time of year. Please add your swg brand and model to your signature so we can figure out how much is actually getting added.

Thanks.

Chris
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Based on the pics, additional info, and earlier history you provided, I'm inclined to believe you have an algae issue that perhaps has gone-on long enough to where it is embedding in the plaster/steps - possibly even black algae. That's why some of it faded when you let the granules sit overnight. The cart filter, other than the green slime you noted, appears to not have any orange, brown, or green staining indicative of copper or iron. I did not see however any updates on trying the Vitamin C tabs or dry acid on the staining. Since you do fill from a well, there is the potential for iron levels to build unless you are exchanging water fairly often.

Regardless, green slime is never good and an indication you need to perform a SLAM Process to remove the algae. Follow that SLAM page carefully for best success. You have a good test kit, so once the SLAM is passed and completed, you'll want to test the FC and pH more frequently. Once the SLAM is completed, continue to evaluate the stains for changes. If they are embedded organic, the elevated FC SLAM level should over time help to lessen them (with brushing). If they are from iron, the Vitamin c tabs will confirm. Not saying the stains are from iron, but also remember that when iron levels increase in a pool, two things tend to irritate that iron to make it precipitate out - a high FC and/or high pH. Another reason to test those two fairly often each week. Let us know how the testing and/or SLAM goes.
Thanks, one question though. How do I lower my FC if I already have the SWG set so low? Should I go even lower? Just seems like something is wrong
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Rich,

FC isn't only dependent on your production %. Sounds like your just not consuming that much. Pretty common with colder water temps this time of year. Please add your swg brand and model to your signature so we can figure out how much is actually getting added.

Thanks.

Chris
Rich,

FC isn't only dependent on your production %. Sounds like your just not consuming that much. Pretty common with colder water temps this time of year. Please add your swg brand and model to your signature so we can figure out how much is actually getting added.

Thanks.

Chris
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