Algae Issues - Green All Summer!

[pmsmith2032]

I'm hoping someone can help me with our algae problem. First I'll provide some background.....we had a 27' above ground pool installed last Spring (2011) and had absolutely no problems keeping the water sparkling clean using bleach. This summer we are using the same method and the pool is constantly turning green/brown. Nothing has really changed.....we're using the same sand filter and pump and testing using the same TF-100 Test Kit.
The only time I've been able to keep it clear is when I keep the FC level near shock level (around 14). As soon as it drops down, the water starts to turn cloudy and within a day or two it is greenish brown. For example, I had the FC up around 14 a couple of days ago. I didn't check it for a few days (the solar cover was on and the daytime temps were in the 70s). I took the cover off yesterday and the water was greenish/brown and there was a layer of greenish/brown "dust" along the bottom. I checked the chlorine and it was at 5.5. I've had the FC level up at shock level for a week and still had issues afterwards. I've even added DE to the sand filter as specified on the website to clean up the water. Below are the other average chemical levels throughout the summer:
pH - 7.5
TA - 120-130
CYA - 40

Could this be mustard algea? Why would I have it this year and not last?

 

[jblizzle]

What are you using to add chlorine?

Did you ever follow the shock process described in Pool School? And not stop until you passed the 3 tests? ... sounds like you are letting the FC drop off of shock level before you should.

Was the pool closed over the winter? What did the water look like when you opened? If algae was present, I am guessing you never completed the entire shock process to kill it off, so it continues to grow at a low level and blooms when your FC drops.

 

[pmsmith2032]

Thanks for the response jblizzle. I am using bleach purchased at Aldis and pouring it into the return inlet of the filter. Like i said, I have kept FC levels up at shock levels for a week (well after the water was crystal clear).

 

[jblizzle]

Wait, where are you pouring the bleach? It should be pour where the water is going back into the pool not into the filter ...

Like I said, did you pass the 3 tests to stop the shock process? It often take much longer than a week. Were you brushing the pool while at shock levels?

The tests:
1. CC not more than 0.5ppm
2. Pass the OCLT (this verifies that all organics/algae are dead)
3. The water is clear (this includes not seeing any algae anywhere in the pool)

 

[pmsmith2032]

Thanks again jblizzle. I am pouring the bleach into the pool where the water returns from the filter (not in it). And yes, I have passed all of those tests.

 

[jblizzle]

Well then try the mustard algae process: pool-school/mustard_algae

Post up your results as you go. Note that you do the normal shock process first until you pass all the tests and then raise to mustard shock level.

 

[pmsmith2032]

Thanks! I would assume that it would not be safe to swim in the pool at the mustard algae shock levels, correct?

 

[jblizzle]

We say it is only safe when the FC is below the normal shock level (and your CC are low and you can see the bottom of the pool and ideally the pH is in range for comfort).