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

[mh_jenkins]

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.

 

[Donldson]

Are you doing the CC test after you do your FC test?

 

[mh_jenkins]

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.

 

[Donldson]

Could you test your FC and CC with your FAS-DPD test and post those numbers up, please?

 

[mh_jenkins]

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.

 

[Donldson]

And what happened with you added the R-0003 to do your CC test?

 

[mh_jenkins]

Added 5 drops of R-0003 to the 10 ml water and R-0870 combination, and the color has a slight yellow tinge to it.

 

[Donldson]

Sounds like your FAS-DPD reagents have gone bad, you will need to replace them to perform the SLAM Process.

 

[mh_jenkins]

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]

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]

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?

 

[AimeeH]

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]

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]

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.

 

[mh_jenkins]

Thank you all!

 

[Casey]

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.