Algae Keeps coming back

[JoeFixes]

Even though we have the pool for 10 years, we have never figured the chemistry thing out. Its pretty frustrating because you think you are doing the right thing, but the water tells you that something is wrong.

Overall the water looks good, nice and clear. Not hazy or murky. The trouble is that the algae always grows back. Last weekend I brought a water sample to the pool store and explained the problem. The guy was very nice and told me that even before testing he will tell me that my alkalinity would be low. He tested it and of course he was right. I needed to add 15lbs of Alkalinity Balance Control. That day I also added half a quart of algae killer and 2 gallons of shock after I scrubbed the algae off the pool walls and floors. That was Saturday. 5 days later and the pool needs to be scrubbed again. Clearly we are not doing something right. I read through pool school again, but I am not sure what I am missing. I ran through all of the tests on my TF-100 and have the following results:

FC 7
CC 15
TC 8.5
ph 7.4
T/A 100
CH 200
CYA 90
pool temp 74°

Tonight I put the other half quart of algae killer in.

I would appreciate someone educating me as to what I am doing wrong.

Thank you

JoeFixes

 

[jblizzle]

First, the CYA is too high ... so you should replace half the water.
Second, the CC are crazy high and that alone would point to requiring the Shocking Your Pool PROCESS when they are > 0.5ppm

Basically, it does not sound like you have maintained a high enough FC level ... not sure how to explain the high CC, but the solution is more chlorine ... of the liquid variety. And forget the algaecides and "killers" ... waste of money.

Read these also:
Defeating Algae
Turning Your Green Swamp Back into a Sparkling Oasis

 

[Richard320]

I think the algae never really left, it just went into hiding to regroup.

Lower CYA to something reasonable, then use the Shocking Your Pool PROCESS

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[JoeFixes]

Ok well here is the "rest" of the story. My 13 year old daughter ran the tests. So now hearing your replies, I cannot be sure that the results are accurate. Replacing half of the water seems pretty drastic for such a large pool, and it may be appropriate if the results are as reported. I just put another bottle of shock in it. I will run the filter tonight and then run the tests myself again tomorrow. Is there just one or 2 tests I could run to verify the CC? or other important factors? Also, my wife seems to think that the skimmer is not catching everything it should/could. We have had a lot of rain recently and the water level seems a bit high. Would too high a water level affect the way the skimmer behaves?

I know these seem to be all basic questions, but as I said we never really got a grasp of the right way to do things.

 

[jblizzle]

The important tests right now to confirm are FC and CC and CYA.

 

[Circles47]

Looks like the CC is 1.5 if the TC is 8.5...

 

[jblizzle]

You are probably right. So, confirm the CYA and that will tell if you need to replace water or start the shock process (CC over 0.5 and the visual algae)

 

[JoeFixes]

Hi Guys,

Okay it has been a few days since I last put a gallon of shock and some algae killer in the pool. The water appears clean and clear. I still need to scrub the walls from the algae that has grown. but honestly its not much. I ran most the basic tests again and this is what I got:

FC 20
CC 0
TC 20
T/A 120
CYA 100

Now lets talk about the CYA. This is the test where you mix 25ml of the pool water with a bit of R-0013. After mixing it, you use the CYA view tube and fill until you cannot see the black dot at the bottom. The numbers are larger for the less fluid in the tube. In fact the measurements start at 100 and go down the more fluid you put in. I know this is a subjective test, but I stop filling when the water becomes cloudy enough not to see the black dot. I would say at the first measurement (100) the black dot is very difficult to see and then at 90 you cannot see it at all. Is this what you consider high?

The test kit does say the normal range is 30-60. I just don't know if my opinion of the black dot being visible is the same as whoever says that 30-60 is normal for most pools. I would love to get your input.

Thank you for the help.

JoeFixes

 

[duraleigh]

You are interpreting the test correctly and, yes, your CYA of 90-100 is too high.

You should plan a drain/refill to reduce CYA to around 50.

 

[jblizzle]

I agree you should replace water. The actual shock FC for your current CYA is nearly double what you currently have in the pool.

 

[JoeFixes]

hi again

so i had some friends over today enjoying the pool. I asked a friend to do the CYA test. Told him nothing about my results and just asked him to read the directions and let me know what he gets for a result. I just wanted to get someone elses interpretation of the test. He runs it 2 times and gets 60 both times.

Is it possible this different interpretation is the right one? It seems crazy to me that such a drastic solution like draining and refilling can be suggested based on a test so subjective.

Thanks for your feedback.


JoeFixes