SLAM not working

[WSS]

Hello:

I have an ungrounded pool of about 20000 gallons. We have had a black algae issue that recently got worse. I had planned to use a copper-based algaecide when I read about the recommendations here to SLAM the pool. I am in day 6 of the process. I have a CYA level around 30, so used 12 ppm as my target level. I have vigorously scrubbed daily with a tell algae brush, and vacuumed several time.

Results? At least a 50% increase in new black algae, mainly on the pool bottom in the shallow end, and on the walls. A major increase in other staining on the pool surface. No idea why there would such an increase (I'm talking about tens of square feet of new stains). Monitoring Cl levels with FAS-DPD test.

I am very frustrated with the results. Suggestions? I am about ready to go the copper route to see if that works.

Thanks for any recommendations.

Attaching photos. First ones are black algae. Last couple are the large areas of new stains that have appeared since I started the SLAM process.

 

[Donldson]

Fast propagation like that tends to be metal staining, not black algae.

Have you used copper algaecide before?

 

[wireform]

Let's get right to it. How are you testing before we can advise.

 

[Bperry]

Hello:

I have an ungrounded pool of about 20000 gallons. We have had a black algae issue that recently got worse. I had planned to use a copper-based algaecide when I read about the recommendations here to SLAM the pool. I am in day 6 of the process. I have a CYA level around 30, so used 12 ppm as my target level. I have vigorously scrubbed daily with a tell algae brush, and vacuumed several time.

Results? At least a 50% increase in new black algae, mainly on the pool bottom in the shallow end, and on the walls. A major increase in other staining on the pool surface. No idea why there would such an increase (I'm talking about tens of square feet of new stains). Monitoring Cl levels with FAS-DPD test.

I am very frustrated with the results. Suggestions? I am about ready to go the copper route to see if that works.

Thanks for any recommendations.

Attaching photos. First ones are black algae. Last couple are the large areas of new stains that have appeared since I started the SLAM process.

Copper based algaecides can cause staining like that, which is why they are not recommended.

 

[WSS]

Fast propagation like that tends to be metal staining, not black algae.

Have you used copper algaecide before?

Not in this pool. We used both copper and silver in our pools in CA.

 

[WSS]

Copper based algaecides can cause staining like that, which is why they are not recommended.

But I have not used the copper yet. I opted to try the SLAM process first, per what I read on this and other groups. Only been using liquid chlorine.

 

[Bperry]

But I have not used the copper yet. I opted to try the SLAM process first, per what I read on this and other groups. Only been using liquid chlorine.

Is the plaster worn away in some of those photos? I mostly meant that switching to a copper based stuff will make more of what you see so switching isn’t going to help. Do you have test logs over the past week? A week isn’t very long for a SLAM with active algae.

 

[WSS]

 

[WSS]

Thought this would be faster than typing in. When I started, I was using a standard DPD test, diluting pool sample 3:1 or 4:1. So readings are my best estimate. My FAS-DPD test came in on 8/30, so started using it. No reading last night due to thunderstorms.

 

[WSS]

Brushing with 8" or so steel brush on pole. I scrubbed all black algae off tile grout above and below water line by hand with 4" algae brush early in the process.

Almost every spot of black algae appears to be in a small pit in the wall. I have not checked the bottom ones.

My biggest concerns are the spread in black algae accelerating during the SLAM, and the rapid appearance of added staining.

 

[WSS]

If the rapid stain increase since I started the SLAM is likely metallic, I see a couple of possibilities. One is that the high levels of chlorine is forcing the metals that were already in the water to deposit, either as metals or water insoluble metal salts. Since I have not added the copper, the only other change that might impact increased metal stains is the extensive use of the stainless steel brush. I would think the SS is stable, but perhaps the friction with the pool walls is generating some metallic iron residue.

Thoughts? Alternatives? Solutions?

 

[Bperry]

If the rapid stain increase since I started the SLAM is likely metallic, I see a couple of possibilities. One is that the high levels of chlorine is forcing the metals that were already in the water to deposit, either as metals or water insoluble metal salts. Since I have not added the copper, the only other change that might impact increased metal stains is the extensive use of the stainless steel brush. I would think the SS is stable, but perhaps the friction with the pool walls is generating some metallic iron residue.

Thoughts? Alternatives? Solutions?

I’m not a fan of the stainless brush unless it’s absolutely necessary. It can be kinda aggressive on plaster but isnt going to stain anything. It’s possible the higher chlorine is forcing the metals (maybe iron) to stain, but those tend to be rust colored. Black and green tend to be copper or algae. I had similar black stuff forming in the crevices of old plaster craters and it was all algae. If you can get down there with a toothpick or chopstick, etc and pick at it, put some on a paper towel and see if it has a greenish tint to it once it’s smushed around. It can be really hard to get algae out of those crevices. It also looks like the plaster is near the end of its life.

 

[TinFoilHat]

I too think you are at the end of the plaster life and it's due for a re-plaster. It may have had a hard life before you and now the divots, nooks and crannies are all hiding your nemesis.

 

[WSS]

Makes sense. The black stuff in the crevices is definitely black algae, as it is dark green. The other stains that have recently appeared are brown/grey (it's hard to be certain when it is at the bottom of the pool). I am surprised at your comments on the SS brush, as the majority of posts I've read on black algae indicated the use of such a brush was essential. I've read that others get into the pool and scrub by hand or use picks, but there are literally more than a thousand if these pits all over the walls (easily over a couple of hundred sq ft), some as deep as 8-10 ft down. No way I can stay down long enough to do any damage, especially with a toothpick and toothbrush as others have described. Not unless I learn scuba and buy the equipment 8^).

I see there are a number of stain removers for iron stains. Is there any consensus or independent testing on which one is most effective?

Thanks for all the helpful responses!

Scott

 

[Lake Placid]

Of your 15 test results, 7 of those fall below the slam criterion of 12 required for a CYA of 30. It’s not surprising you’re seeing new propagation. Not to mention you were estimating with a very likely high error factor in 6 tests. 7-8 tests look like actual FAS DPD tests. Of those, 4 are under SLAM threshold, with 3 well under (6 ppm or so). Double down, start to SLAM for real, test frequently, add frequently, scrub, and maintain a residual of chlorine that will kill the algae. Yes, your plaster looks worn and near EOL, but I don’t think you’ve given the process a legitimate chance by the methods you are currently employing. You seem to want to look elsewhere (Algaecide, metal salts, friction, et al) when there’s an obvious answer in front of you.

 

[WSS]

Let's get right to it. How are you testing before we can advise.

Sorry, I missed this comment earlier. I have a couple of pool test kits. One uses a DPD Cl test, the other OTO. Both only go to 5 ppm Cl. I found the color differences to be easier to visually distinguish 2, 3, and 5 ppm with the DPD test. Online chats recommended a PAS-DPD test for the higher Cl levels used during the SLAM process, so I ordered one. But I started the SLAM before receiving it. So I diluted the pool water with bottled water using a 6 mL syringe for accuracy. I mainly did a 1:2 and 1:3 dilution pool:bottled, then multiplied the Cl result by 3 and 4 respectively. Not highly accurate, but it was a start. When I got the PAS-DPD test, I switched. To save on titrating reagent I am using 5mL pool water, so each drop is 1 ppm. I did not feel the need to know the level to the nearest 0.2 ppm.

Does that help?

 

[WSS]

Of your 15 test results, 7 of those fall below the slam criterion of 12 required for a CYA of 30. It’s not surprising you’re seeing new propagation. Not to mention you were estimating with a very likely high error factor in 6 tests. 7-8 tests look like actual FAS DPD tests. Of those, 4 are under SLAM threshold, with 3 well under (6 ppm or so). Double down, start to SLAM for real, test frequently, add frequently, scrub, and maintain a residual of chlorine that will kill the algae. Yes, your plaster looks worn and near EOL, but I don’t think you’ve given the process a legitimate chance by the methods you are currently employing. You seem to want to look elsewhere (Algaecide, metal salts, friction, et al) when there’s an obvious answer in front of you.

Okay, understood. I was testing early AM, near sunrise and just before sunset. The drops you mention were the first overnight, when the algae was fresh, and during daytime, when the sun has its impact. So it seems that I need to test more often during the day. I assumed, apparently incorrectly, that drops were to be expected during the process.

As for the alternatives, I had originally found copper was the most recommended in early searches, then I found the discussions on the SLAM process and decided to go that route. I'll restart and follow your recommendations. Thanks again.

 

[mknauss]

If dealing with Black Algae - which is actually a bacteria -- please read Black Algae

 

[Bperry]

Sorry, I missed this comment earlier. I have a couple of pool test kits. One uses a DPD Cl test, the other OTO. Both only go to 5 ppm Cl. I found the color differences to be easier to visually distinguish 2, 3, and 5 ppm with the DPD test. Online chats recommended a PAS-DPD test for the higher Cl levels used during the SLAM process, so I ordered one. But I started the SLAM before receiving it. So I diluted the pool water with bottled water using a 6 mL syringe for accuracy. I mainly did a 1:2 and 1:3 dilution pool:bottled, then multiplied the Cl result by 3 and 4 respectively. Not highly accurate, but it was a start. When I got the PAS-DPD test, I switched. To save on titrating reagent I am using 5mL pool water, so each drop is 1 ppm. I did not feel the need to know the level to the nearest 0.2 ppm.

Does that help?

Just to make sure. The FAS-DPD test uses 10ml of water or 25ml. The 10ml gives you 0.5ppm accuracy and is the recommended size by TFP. The 25ml sample gives you 0.2ppm accuracy and isn’t necessary.

Using 5ml sample gives you only 1ppm accuracy and the tolerance is also +\- 1ppm and is only recommended when you are running out or reagent.

All that to say, make sure you are counting drops and using the right multiplier for your sample size.