Cloudy after shocking

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spaige

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Jan 20, 2009
48
Atlanta, GA
I just went through a big battle with algae and now have a cloudy pool. I read in one of the "Pool School" articles that this would happen. However, my cloudiness seems to be going longer than was indicated in the article, i.e. a week. Could I have a different issue?

My Ph is 7.5, FC is 28, Alk. is 80, CYA seems to be a little over 100- my test kit doesn't read over 100 so I'm estimating. My pool is 30,000 galllons and is vinyl. Thank you.

spaige
 
Welcome to TFP!

I see two possible issues. The first issue is that you don't really know just how high your CYA level really is, and therefore can't be sure you have your FC level high enough. The standard CYA test can read levels far higher than 100 as 100 sometimes. An FC Level of 28 is good for shocking when CYA is up to 120 or perhaps a little higher. But if your CYA is actually significantly higher than that it won't be enough. You can try diluting a sample of pool water one to one with tap water and then doing the CYA test on that. If you multiply the result by two you will get an approximate CYA level. Doing the test that way is much less accurate, but it will be enough to indicate if your CYA level is only a little over 100 or is closer to 200 or even higher.

The other question is about your filter. What kind of filter do you have? Has the filter pressure been rising? And have you been backwashing or cleaning the filter as needed?
 
IF your pool water is cloudy you will not get an accurate CYA test since it is a turbidity test (measures the cloudiness of the water.)

What did you shock with? Liquid chlorine (bleach) or cal hypo (powdered shock)? Cal hypo can also cloud the water.
 
I have a sand filter and I have been backwashing frequently. The pressure does not seem to be rising on the filter especially now that the water is no longer green. I am shocking with 6% bleach. Thanks very much for the quick responses.
 
spaige,

Unless you started out lowering the pH to around 7.0 before you added a hypochlorite source of chlorine (e.g. bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite), I doubt that your pH is really at 7.5. If your pH started out at 7.5 and you added 28 ppm of chlorine, this would raise the pH very high to almost 8.9. If you have even 100-150 ppm Calcium Hardness, then the water could become cloudy from over-saturation of calcium carbonate. What sort of test kit are you using? Do you have test strips or a Taylor K-2006 test kit or TF100 test kit?

I see that you were using 6% bleach. Can you also tell us the Calcium Hardness (CH) if you know it? Also, what is your pool temperature? Did you happen to test the CYA level at any time before the water was green or got cloudy and was it >100 ppm at that time? Do you know how the Cyanuric Acid (CYA) level got so high? Were you previously using Trichlor tabs or Dichlor granular/powder?

I suggest two things. First, see if your Free Chlorine (FC) level is holding overnight -- not dropping by more than 2 ppm FC at the most given the high chlorine level (normally we look for a <1 ppm FC drop, but your FC level is pretty high). If it's holding, then dilute the pool water with fresh water, either through multiple partial drain/refill or continuous dilution. You'll need to do that anyway to lower the CYA (IF it really is that high) and this will remove some of whatever is cloudy as well. It will also dilute your chlorine to lower the FC which should also lower the pH as well (IF it's actually high and you have a false reading from a test strip).

By the way, if you take a sample of pool water and put it in the CYA view tube, is it cloudy enough to obscure the black dot and if so, at what level?

Richard
 
Thank you Richard. This morning my calcium is 200, chlorine is 22 and PH is indeed 8.0 or better. One interesting thing this morning is that I'm getting a yellow endpoint on my alkalinity test. I have never seen this before.

With regard to your question about cloudiness in the small vial and being able to see the black dot; I can see the dot clearly all the way to the top--no obscurity.

My test kit is a Taylor 2006. My CYA increased from the shock I used last season and some tablets I used for a while when the weather turned cold. I have a SWG. I had a problem with mustard algae last summer and kept getting conflicting advice from pool shops about how to handle it. Ever since my water has not been clear. Thank you very much for your assistance.
 
Spaige,

You are doing the CYA test incorrectly. No obscurity means no CYA.

Look at the gradations on the side of the CYA view tube and, if you have no obscurity, will find your CYA is twenty or less.

The more CYA that is in your pool, the less mixture you will put into the view tube to obscure the dot.
 
Thanks Dave, but look at Richards response. He suggested that I do the CYA test with water alone just to see if the dot was obscured. I did not add the test chemicals to the water to perform the test. Richard was just wondering how the water looked in the vial without actually doing the test. Thanks.
 
spaige said:
One interesting thing this morning is that I'm getting a yellow endpoint on my alkalinity test. I have never seen this before.
Click to expand...
That is an interference from your high FC levels. The chlorine beaches out one of the indiactor dyes so your test goes from blue to yellow instead of green to red. The test results are still valid. You could add an extra drop or two of thiosulfate (R-0007) at the start of the test to compensate for this.
 

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Steve,

OK, since you have an SWG you're probably going to want to end up with 70-80 ppm CYA anyway. So you will want to dilute some, but it's hard to know by exactly how much, especially since your water is cloudy. Though the water doesn't seem to look cloudy in the view tube without CYA reagent (melamine), the cloudy particles may still interfere with the CYA test. So perhaps some dilution is in order, but not too much. I'll bet you could dilute by 20% of the water volume and not overdo it.

If your Free Chlorine (FC) level seems to be holding overnight, then I'll bet you can let your FC drop to around 10 ppm FC and still be OK preventing further algae growth. As it drops, see if the water starts to look more clear. If it does, then the cloudiness is over-saturation of calcium carbonate due to the high pH from the high chlorine levels. You might see the pH starting to creep below 8.0 as the FC gets closer to 10 ppm, depending on what the pH was when you started. If the water is close to clear, you could then add a little acid at that point to bring the pH down a little further, but let's first see how things go as the FC drops.

What you are going through is one reason why very high CYA pools usually require partial drain/refill as a first step. Not only do they require very high levels of chlorine to kill algae, but such high chlorine levels will make the pH rise and tend to cloud the water. In general, whenever adding more than about 10 ppm FC to a pool, one should lower the pH first if it's 7.5 or higher to start with.

Richard
 
Thanks Richard. What you are saying makes perfect sense. Over the last couple of days the water has gotten clearer which I think is in large part due to the fact that I have been replacing the water. It's raining here today so I'm going to see where everything stands tomorrow but things do seem to be improving slowly.

When you say, "over-saturation of calcium carbonate due to the high pH," is there any way to prevent this other than keeping the pH down? I assume this has to do with the amount of calcium in the water, correct?

Again, I want to thank you for your help.

Steve
 
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