Reoccurring green algea

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Oasisdave2

Member
Apr 6, 2017
21
HEMET, Ca
So I have been having issues with reoccurring green algae every few days. I purchased the TF-100 and tried doing the tests but ran into some problems which I will do my best to explain. first, though, I figured a little background information might be helpful. My pool is a kidney shape 35' long and 16' at the widest point with a 500 gal spa attached with a spillway into the pool. I believe the total pool volume to be approximately 15,000 gal. I have been using granular Chlorine which was recommended by a friend of mine that used to build pools before he retired. I will post a picture below of the active ingredients. I also used to use a chlorine floater in my spa with tablets with the same ingredients from the same manufacturer but since the pandemic have been unavailable and I switched to the ones carried at Costco which I am starting to believe may be part of the issue with my pools chemistry and the algae problem.
IMG20220704113323copy.jpg

On to the testing results

When I attempted to run the Chlorine Drop Test the sample did not turn pink so there was no Chlorine and was confirmed when I ran the daily CL test which also came back as 0. I tried continuing on to the FC but had added 35 drops and the water was not getting any clearer (If possible it seemed to be getting cloudier), so I discontinued the FC and CC test as I am guessing that if there is no Chlorine you basically can't run the rest of the Chlorine Drop Test? Please correct me if I am wrong here. The CYA test was also concerning as I couldn't see the black dot after the tube was only filled to about 1/4 inch BELOW the 100 mark. To me, this doesn't make any sense as I added about 3 cups of Chlorine granules three days ago. If the CYA is this high shouldn't there be some chlorine showing when I test instead of the zero reading I got when testing today? below are the rest of the results (The Calcium is concerning to me as well.

FC - Not Completed
CC - Not Completed
CL 0.0
PH 7.4
TA - 110
CH - 650
CYA - 1/4 inch below the 100 mark
Phosphates - 250 PPB (Test done with Taylor K-1106)

I could really use some advice on what to do next. I first thought I would need to add conditioner since the chlorine I add seems to be evaporating so quickly but the test showed that mine is apparently really high but that doesn't line up with the zero chlorine reading as far as I understand. Thank you all for any advice you can give, and please let me know if there is any other information you need.
 
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Correct, the FC is zero.
The CYA is very high. Very very high. You will most likely need to do a complete exchange of the water to fresh.,
To confirm, mix the pool water and tap water 1:1. Then use that sample for the CYA test. If the dot still disappears with water below the 100 line, time to exchange.
 
Oh boy, that's not going to be easy in SoCal with the drought. I know that CYA causes Chlorine to become less effective when it is high but wouldn't it still keep the Chlorine in the pool?

Edit: So I ran the CYA test again using 1/2 tap water as mknauss suggested and the dot disappeared just shy of the 100 mark
 
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Try the cya test again with a 2:1 tap: pool water ratio. Multiply by 3 for final result.

You will likely need to exchange the water in the pool or get RO treatment to take the CYA down. Constant use of trichlor both in shock and in pucks is making your CYA raise to unmanageable levels.
 
So a few more questions. I'm assuming after a drain and refill I will need to do the slam process to eliminate the algae? Also do you guys think that maybe draining 1/2 or 3/4 of the water be ok or do you think it's so bad that I should just start as fresh as I can?

Should I brush the new growth of algae before I start draining so it gets pumped out or does that not really matter since I will be doing the slam anyway?

Anything further I should do before draining and what should the process be after the refill? Sorry so many questions but I really want to get this right.

And thank you, thank you, thank you for the advice so far!
 
Oasisdave2 said:
maybe draining 1/2 or 3/4 of the water be ok
Click to expand...
Have you done the extended test for CYA as suggested above? If that shows a CYA of 200 ppm or higher, then a full exchange (I would not drain a plaster pool in the summer - read Draining - Further Reading) is needed.

Oasisdave2 said:
Should I brush the new growth of algae before I start draining so it gets pumped out
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Would not hurt. But a SLAM after refill is still suggested.
 
What is your pool finish? It may be safer to do a no-drain water exchange.

If you get a 180-210 result in the 2-1 diluted test then a 75% drain or exchange would take you down around 50, which is do-able for a SLAM. Above that and it’s hard to say.
 
2-1 diluted test came out to 60 so right at the 180 mark. The pool surface is white plaster with blue sand added for color (can't remember what the builder called it).

I looked at the info for the no-drain water exchange and one thing I can definitely do is get the pool water warmer than the fill water. We have the plastic 'solar' heating panels on our roof that I can divert the water through and we are expecting temps from 87° tomorrow to the low to mid 90's over the next 10 days and the forecasts on my weather app are usually lower than what we end up getting. The question would be where to put the pump and how to refill. My refill is at the deep end as well as my skimmer.
 
Get the CH of both waters and the salinity of the pool water and complete the calculation in the Wiki I linked to.
 

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Oasisdave2 said:
So I have been having issues with reoccurring green algae every few days. I purchased the TF-100 and tried doing the tests but ran into some problems which I will do my best to explain. first, though, I figured a little background information might be helpful. My pool is a kidney shape 35' long and 16' at the widest point with a 500 gal spa attached with a spillway into the pool. I believe the total pool volume to be approximately 15,000 gal. I have been using granular Chlorine which was recommended by a friend of mine that used to build pools before he retired. I will post a picture below of the active ingredients. I also used to use a chlorine floater in my spa with tablets with the same ingredients from the same manufacturer but since the pandemic have been unavailable and I switched to the ones carried at Costco which I am starting to believe may be part of the issue with my pools chemistry and the algae problem.
View attachment 432000

On to the testing results

When I attempted to run the Chlorine Drop Test the sample did not turn pink so there was no Chlorine and was confirmed when I ran the daily CL test which also came back as 0. I tried continuing on to the FC but had added 35 drops and the water was not getting any clearer (If possible it seemed to be getting cloudier), so I discontinued the FC and CC test as I am guessing that if there is no Chlorine you basically can't run the rest of the Chlorine Drop Test? Please correct me if I am wrong here. The CYA test was also concerning as I couldn't see the black dot after the tube was only filled to about 1/4 inch BELOW the 100 mark. To me, this doesn't make any sense as I added about 3 cups of Chlorine granules three days ago. If the CYA is this high shouldn't there be some chlorine showing when I test instead of the zero reading I got when testing today? below are the rest of the results (The Calcium is concerning to me as well.

FC - Not Completed
CC - Not Completed
CL 0.0
PH 7.4
TA - 110
CH - 650
CYA - 1/4 inch below the 100 mark
Phosphates - 250 PPB (Test done with Taylor K-1106)

I could really use some advice on what to do next. I first thought I would need to add conditioner since the chlorine I add seems to be evaporating so quickly but the test showed that mine is apparently really high but that doesn't line up with the zero chlorine reading as far as I understand. Thank you all for any advice you can give, and please let me know if there is any other information you need.
Click to expand...
To answer your question on the testing. The chlorine level only needs to be checked using the FAS-DPD, which is the powder and the reagent that turns the water pink when chlorine is present. If it doesn’t turn pink after two scoops of powder, there is no chlorine. You’ll find it easier to use the 10ml sample as well so each drop is 0.5ppm of FC. Don’t bother with the OTO test (yellow color comparator).

For reference, normal healthy uncovered pools will consume about 2-4ppm of chlorine per day. The other replies have you for the rest of it.
 
Yeah, I wouldn't heat the pool. I'd leave it colder / same temp as the incoming water, add to the top and pump from the bottom. There's probably a lot of dissolved items in the pool water that will increase the density. But best to get a pool store to do a salinity test and do the calc in the article. :)
 
I really suggest you read the Wiki that was linked. You really should do the calculation. Also it describes where to add water and pump from.
 
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mknauss said:
I really suggest you read the Wiki that was linked. You really should do the calculation. Also it describes where to add water and pump from.
Click to expand...
I will do the calculation, hopefully tomorrow after work. I will post what the numbers are and also do the calculation. I am confused on adding the water to the skimmer though. I would think it would just back up into the pool?
 

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