Using TF-100 kit and during the hottest part of the summer (July-Aug) getting Green Algae

mh_jenkins

Active member
Jul 27, 2014
25
Lexington, SC
I have been using the TF-100 kit and have been checking and maintaining daily the water chemistry. Last week the pool started getting green at the bottom and is steadily getting more green algae. Here is my current water chemistry. pH=7.4 (have kept it between 7.2 and 7.5), TA=100 (have kept it at 100), CYA=40 (have kept it at 40, no higher), Cl>5 (have kept it between 4 and 10 but usually about 5). I used the R-0870 to do the Chlorine Drop Test and it showed 0 FC. (the R-0870 is about 3 years old and kind of stuck together so not sure if it still works or not).

My pool, I think, is acting like the CYA is over 100 but it is 40, like it is locked. Help? What am I doing wrong? I want to not get in this situation, what am I missing? I know how to get the green out, but don't want to get to this point.
 
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mh_jenkins

Active member
Jul 27, 2014
25
Lexington, SC
I usually do not do the FC test only the K-1000 basic test daily and keep the CL >4. I did the FC test because I knew there was a issue at hand. Additionally just tested the water temperature with a very accurate thermometer... it is 93 F. The chemical I am using for the CYA test is R-0013 taylor.
 
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Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,883
NW Ohio
Could you test your FC and CC with your FAS-DPD test and post those numbers up, please?
 

mh_jenkins

Active member
Jul 27, 2014
25
Lexington, SC
I just went out to the pool. I put a heaping spoon full of R-0870 into the 10ml of pool water and it did not turn pink. I then tested the cl with the K-1000 test kit and it is reading >5. The PH just spiked from 7.5 this AM and now 8.2 so will add M acid.
 

mh_jenkins

Active member
Jul 27, 2014
25
Lexington, SC
Ok I can do the SLAM process... I appreciate your help, still need to know what I have done wrong to get in this situation? I have kept the CL >4 PH around 7.5, and CYA at 40 all summer. Otherwise, there is something to the process requiring SLAM every summer. or is SLAM required every summer?
 

Donldson

TFP Expert
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In The Industry
Jun 12, 2009
3,883
NW Ohio
Can't say what went wrong. The OTO test only tests for Total Chlorine and is not precise nor accurate enough to draw any conclusions from. Without a log of FAS-DPD results it is impossible to draw any conclusions. I guess if you want an answer it is that you haven't been keeping track of your FC and CC which would have clued you in to a problem arising long before this point. The OTO test is for a quick "yep, chlorine still there" daily test, but it does not replace the need to check your FC and CC properly every few days to confirm nothing has gone awry.
 

mh_jenkins

Active member
Jul 27, 2014
25
Lexington, SC
That makes since. Yes the R-0870 is a purple/brown color so it is probably bad. Does the pool temperature at 93% have anything to do with the chlorine lock?
 
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AimeeH

LifeTime Supporter
TFP Guide
Apr 2, 2012
2,028
Columbia SC
There
That makes since. Yes the R-0870 is a purple/brown color so it is probably bad. Does the pool temperature at 93% have anything to do with the chlorine lock?
really is no such thing as "locked" or "chlorine lock" your chlorine needs to be high enough according to the CYA chlorine relationship at all times to prevent algae. So at some point yours must have dropped too low for your CYA.

You will need to follow SLAM process. But first, can you describe how you're conducting your CYA test to get 40?
 

mh_jenkins

Active member
Jul 27, 2014
25
Lexington, SC
Guess the 93% pool water temp makes no difference? To determine the CYA I use a red tipped bottle in the TF-100 kit, fill up to the bottom of the label with water, then fill to the top of the label with R-0013 taylor solution, shake then start to fill the CYA view TUBE till I cannot see the black dot at the bottom. Read tube line to determine the CYA.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,027
Laughlin, NV
The 93 degree water does not make all that much difference, once you are above 70F or so algae can grow. The warmer temperature means you are getting more UV impact on your pool water, which consumes FC.

Elevated water temperature can degrade CYA quicker. So be sure to test that level at least monthly.
 

Casey

TFP Expert
LifeTime Supporter
Apr 16, 2007
10,916
SW PA
If your pool is green you need chlorine. You've been on the lower end for an undetermined amount of time and algae took over.