ph keeps falling

mlulm

Member
Aug 26, 2008
17
I'm been helping a friend for the last year who's pool had way too much alkalinity and stabilizer. We have gotten the alk. down to about 200. A couple of weeks ago we added some acid and aireated the ph back up and took the aireator off. In a day or two it started getting cloudy and the ph had fallen to 7.0. This has happened twice. What is causing this?
 

JasonLion

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May 7, 2007
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Silver Spring, MD
You should post a full set of water test results. There is much more we can tell if we have that information.

Keep in mind that the PH test will read higher than actual when the FC level is above 10. Depending on just how high the FC level was, the PH could appear to be falling as the FC level comes down and the PH test gets closer to being accurate, when the PH was actually low all along. Falling FC levels could also allow algae to get started, causing the water to cloud up. But I'm just guessing and can't really say without seeing water test results.
 

mlulm

Member
Aug 26, 2008
17
Right now its
fc 14
ta 200
ph 7.0
CYA >200
borates 50

The first time it got cloudy he started airating again and that cleared it up.
He just raised the fc from about 4 last night.
Can low ph cause it to be cloudy?
 

JasonLion

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May 7, 2007
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Low PH won't directly cause cloudiness, but it can cause the chlorine to be less effective, which can let algae get started, and that can cause cloudiness.

With FC at 14, the PH will read a little higher than it actually is, so the actual PH is below 7.

Do you know what the CYA level is?
 

mlulm

Member
Aug 26, 2008
17
Using test strips the cya looks to be above 200.
Using drops for the other readings.
He stopped using stabilizer last year and used a lot of acid in the last year to bring the ta down from about 375.
 

mlulm

Member
Aug 26, 2008
17
Low PH causing the chlorine to be less effective could be the problem.
But what causes the ph to drop so fast when he stops aireating?
 

JasonLion

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May 7, 2007
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With CYA at 200, you never want to allow FC to fall below 15. So the FC level has been way too low most of the time. So the cloudiness is almost certainly from algae.

As I said earlier, the PH is probably staying more or less the same and the FC level is falling. As the FC level falls it interferes with the PH test less and less and the actual low PH level becomes apparent.

I don't think you are going to be able to make any real progress until you get the CYA level down dramatically lower. Managing a pool with CYA around 200 is nearly impossible.
 

mlulm

Member
Aug 26, 2008
17
Is it possible to add a couple of drops of chlorine nutralizer to the ph test to get a more accurate reading?
 

PaulR

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Jan 11, 2009
1,966
Cupertino, CA
If you're using the Taylor pH test (R-0004 or R-0014) it already has some neutralizer in it. Adding more is counterproductive because the neutralizer itself will affect pH.
--paulr
 

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