Baffled by cloudiness that seems to clear every now and then

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poolcool

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May 1, 2010
15
A very brief history. Two weeks ago I raised CH from 150 to 300. I then did a citric acid stain removal with 10 lbs in 20K gals (an amount that I now think was overkill). I then raised borates to about 40.

I have been having cloudy water since the acid treatment that sometimes seems to clear up but quickly reappears. It’s as bad as ever when it reappears.

But here's something that also seems very weird. The spa receives the same water return as the pool and overflows into the pool. Sometimes the spa is virtually crystal clear but the pool is cloudy. Other times the spa appears cloudy but the pool is fairly clear. Then sometimes they’re both cloudy and very infrequently both clear.

If I look closely, it appears that the tiniest of particles are moving about in the pool. If I fill a glass with the pool water it appears that some the particles are actually the tiniest of bubbles. However, when I compare it to a glass of tap water, I can still see a lot of tiny particles in the pool water after the bubbles dissipate.

The chlorine demand has been immense. I’ve added over 30 gals of 6% bleach and I’m running my SWG at a rate that would easily keep over 2 ppm under normal circumstances and the FC still drops to zero. FC has dropped from almost 5.0 to 3.4 in the last 2 hrs. I don't think that the FC is ever 0 for more than a few hours at a time. The pump and SWG are running pretty much 24/7.

I added some clarifier (cationic polymer) this morning with no positive effect so far.

Test results are as follows:

FC 0 to 5 depending on how soon the test is conducted after adding bleach.
pH 7.5 and slowly rising (I add muriatic when it reaches 7.7)
TA 110 and slowly rising (drops slightly when I add muriatic)
CH 300 steady
CYA 40
Salt 3400
Borates 40

This is a real head scratcher but any ideas would be most welcome.
 
Quote "FC 0 to 5 depending on how soon the test is conducted after adding bleach."

What is your CC reading? To me the above statement make it seem to me that you have organics eating away your FC and may need to shock.
 
First, you should never ever let the FC level go below 2. If you are having trouble maintaing a consistent FC level then it is time to shock the pool. Continue shocking until you lose 1 ppm of FC or less overnight.

When you are done shocking, raise the CYA level up to 80.

The cloudiness is algae, which never really gets going because of all the chlorine you are adding, but also never really gets all killed off because you aren't bring the FC level up high enough.
 
Thanks everyone for the responses. They all sound logical based on the circumstances and I was kind of heading in that direction so it sort of confirms my suspicions.

I have had a concern that the metal staining might return with heavy shocking but I’ve also been backing off on using metal control because I’m afraid of an overdose of HEDP.

Questions:
1. I would like to use 6% bleach to shock. How much should I add each time to shock 20K gals? What ppm am I trying to achieve?
2. Any thoughts on the metals concern vs. shocking?
3. The pH rising vs. spa overflow makes sense but the spa can’t be stagnant and it can’t be allowed to drain down either. Other than finding the exact flow balance, is there anything else that I can do?
 
OK, the pool has cleared up completely after two rounds of 16 ppm FC shocks, but the metal stains appear to be returning so I added 2 qts of HEDP in the hopes that it can catch them and even remove them while they are still fairly light.

I brought the FC up to 16 at 10:30 pm last night and it was still 16 at 7 am this morning so it held up well overnight. However, during the day it has dropped to 1.5. Current readings are as follows:

FC 1.5
CC 0.5
TC 2.0
pH 7.4 (added a half gal muriatic last night to try to bring the TA down)
TA 130 (was 135 before the muriatic)
CH 290
CYA 45
Borates 40

The pump and SWG are running 24/7. The filter dP has risen only by about 8% since the last backwash about 2 wks ago.

So, although I am very happy that the water is clear, I'm bummed that the stains are returning and am therefore scared to add too much more chlorine. So, my latest round of Q's are:

1. Considering that the staining is starting to return, what should I do about the FC?

2. Why is the TA rising? It went from 95 to 135 in the last 8 days without adding any baking soda or borax and I used boric acid to get the borates up to 40 ten days ago.

3. Why is the FC falling so much during the day with 45 ppm CYA?

I really appreciate all the help I've gotten from TFP.com and my trust in your advice is pretty high, so thanks again.
 
The sequestrant is probably consuming some of your chlorine. Some brands are better about that, some worse.

High PH & FC levels both tend to cause stains to return. This can be avoided if you have enough sequestrant in the water, but it takes some experimenting to figure out what the right amount is. At the first sign of stains returning you should add more sequestrant and lower the PH a little.

I don't know why TA is rising. TA will go up as PH goes up, but not by that much. Try wiping the dropper tip with a damp cloth/tissue before doing the TA test and after every 5 drops and see if that makes any difference.
 
Such a significant drop cannot be just from sunlight, especially with CYA in the water. Are you adding anything to the water during the day? Is there some kind of animal drowning daily in your skimmer? Oxidizing a small critter with eat up all of your chlorine very quickly.

Just a tip for when you are done. If you're going to go to 80 ppm CYA from 45-50, this will lower your pH by around .5 if I'm remembering the numbers correctly, so wait until your pH is up. This effect can also be used to reduce the amount of muriatic acid you'll need to add if you use borax to add borates.
 

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I checked the tests again and everything is the same except that the TA did go from 130 to 125 when I wiped the dropper tip but how accurate is the test at that point? It starts to change at 11 drops, changes to a little more red at 12 drops and completely to red at 13 drops. So I interpolate the result to 125. Is that the correct way to do a TA or similar test? The Taylor salt test says to stop immediately upon the first slightest change but they make that point only with the salt test.

I checked the skimmers and there were no critters but we did have a small amount of rain earlier today so there were some pine needles and other organics. The only critters that I ever get are the rare small snake or gecko.

This is what I plan to do tonight. I'll raise the FC to 4 per the pool calculator and I'll add another qt of HEDP metal control. Then, I'll have a glass of beer, read the paper and go to bed. Let me know if any part of the plan isn't satisfactory (except the beer part because that's a done deal :cheers: ).

Thanks again.
 
For the Taylor TA test (and CH test, for that matter) you add drops until the color stops changing, and don't count the first drop that caused no change. So if you saw a change after drop 12 and drop 13 but not drop 14, that would be 13 drops or 130. The salt test works differently.
--paulr
 
I'm pretty sure that the pool was sufficiently shocked because CC is only about 0.2 and I'm losing 1 ppm or less of FC overnight.

I don't know why I lost so much during the day yesterday with 45 ppm CYA, but I could tell that it had been raining when I got home from work, but it was probably less than 1/2".

Does rain affect the FC other than the dilution factor?

I added enough bleach last night to bring the FC up to about 4 per the pool calculator and it was 3 this morning.

Should I shock again?

I have no problem with shocking other than the metal stains. I still wish that there was a sequestrant test kit so I wasn't just blindly adding it.
 
The rain it's self doesn't do a whole lot. But rain is often accompanied by blown in dust and debris, which can sometimes use up a lot of FC.

There probably isn't any need to shock, unless the FC loss continues.
 
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