Very strange chlorine problem

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S

sefton

0
Sep 5, 2011
6
I have a very strange problem. Both the total and free chlorine are sky high and remain that way, even if I don't add any chlorine.

History:
My pool was green with algae and at the time the PH and alkalinity were both very low (off the scale). I shock treated the pool with 6 cups of granule chlorine and the next day I added 2 Kg (about 4.4 lbs) of "Alkalinity up". After a few days the alkalinity and ph were still extremely low. I then added another 2 Kg of "Alkalinity up" and the alkalinity and ph were now just below normal. The pool however was still green, so I shock treated it again with HTH shock-it which is chlorine based. After this the total chlorine and free chlorine remained super high (off the scale), even after 2 weeks of no chlorine added, in very sunny weather.

Here are the details:
Pool volume: 60,000 litres (15,850 US gallons)
Total hardness: 250 ppm
Total chlorine: > 10 ppm
Total Bromine: > 20 ppm
Free chlorine: > 20ppm
pH: 7.1
Total Alkalinity: 70 ppm
Cyanuric acid: 40 ppm
Water color: turquiose and very cloudy

The above were measured using an AquaChek7 strip
I have confirmed the total chlorine reading using an AquaCheck strip and also an HTH test kit.

I would appreciate it if someone would please tell me what is happening and what I should do.
 
Wow. Where to start...
Well, foremost, I suspect the test strips to begin with. They are notorious for wildly inaccurate results.
Also, total chlorine (TC) = free chlorine (FC) + combined chlorine (CC), thus FC cannot be higher than TC, so again, I suspect some error in testing or transcription.
Moving along...

Not sure what the composition of the granular chlorine which you first added, but assuming 1) that it was dichlor and 2) that you use 8oz cups, 6cups (48 oz) of Dichlor should have raised the chlorine level of 15,850 gallons of water by over 13000ppm, according to the pool calculator. That is a **VERY** high chlorine level.
I assume that the HTH shock-it is calcium hypochlorite, and it packs a good concentration of chlorine, but without knowing how much you have added, we cannot estimate what impact it would have had.

Chlorine will normally drop over time as it is consumed by the sun's UV rays, but the cyanuric acid helps to prevent that loss. Also, 48 ounces of dichlor would have added 12000ppm of CYA, so there may not be a lot of UV loss. It will also drop as it gives up its life fighting organic nasties in the water, but honestly, I cannot conceive of there being any in 13277ppm of FC. I'm at a loss as to how to estimate how long it might take to drop from levels like that. It may make more sense to do a partial drain and refill of the pool water.


Lastly, that ph of 7.1 is still pretty low, and high chlorine levels will tend to skew ph readings toward the high side, at least the liquid color-comparison tests - not certain about strips, but as mentioned above, we've seen so much error w/ strips that we do not trust them at all. Your ph likely still needs to come up a bit, perhaps to around 7.5 - you'll want to keep a good eye on it as the chlorine levels drop.
 
Ohm_Boy said:
Not sure what the composition of the granular chlorine which you first added, but assuming 1) that it was dichlor and 2) that you use 8oz cups, 6cups (48 oz) of Dichlor should have raised the chlorine level of 15,850 gallons of water by over 13000ppm, according to the pool calculator. That is a **VERY** high chlorine level.
Click to expand...
Ohm_Boy, I think you used 15 gallons instead of 15000 gallons. From pool calculator for 15000 gallons, starting at 0 ppm FC, adding 48 ounces of dichlor, I get 13 ppm FC and a rise of 12 ppm CYA.:-D

sefton said:
The above were measured using an AquaChek7 strip
I have confirmed the total chlorine reading using an AquaCheck strip and also an HTH test kit.
Click to expand...
It seems unlikely that you have any chlorine in there if you have not added any in weeks. Is there a pool store around that you could get an independent test?
sefton said:
he pool however was still green, so I shock treated it again with HTH shock-it which is chlorine based. After this the total chlorine and free chlorine remained super high (off the scale), even after 2 weeks of no chlorine added, in very sunny weather.
Click to expand...
How much did you add this time? Be careful with this stuff, it adds calcium. What kind of pool surface do you have? Better yet , put your pool/equipment specs in your sig.
 
Thanks everyone for the quick and detailed responses, I really appreciate it.
Ohm_Boy said:
Also, total chlorine (TC) = free chlorine (FC) + combined chlorine (CC), thus FC cannot be higher than TC, so again, I suspect some error in testing or transcription.
Click to expand...
The test strip that I used had a maximum scale of 10ppm for the TC and a maximum scale of 20 for the FC, and in both cases they were off the scale, which is why I quoted TC as >10ppm and FC as >20ppm.

Ohm_Boy said:
assuming that you use 8oz cups
Click to expand...
Yes the cup is about 8oz.

frogabog said:
Sefton, was the granular chlorine dichlor or something else?
Click to expand...
I'm not sure what dichlor is, but on the container it says "active ingedient: calcium hypochlorite"

linen said:
Is there a pool store around that you could get an independent test?
How much did you add this time?
What kind of pool surface do you have?
Click to expand...
I will take a sample to a pool store and post the results here - this may take a few days. I added 2 packs of shock-it, and I would guess that they were about 1.5 lbs each. I will check the next time I'm at the store. The pool surface is fibreglass - I think :)
 
Yeah, the test strips tend to be useless. I would get a good test kit (see my sig). 3 lbs of 48% cal-hypo would only raise FC by 11. My guess is you have no FC in the pool now, I would dose it using bleach/liquid chlorine using the poolcalculator.com. See: http://www.troublefreepool.com/pool-school/shocking_your_pool. However, to continue the shocking process, you will need a good test kit.
 
Ohm_Boy, I think you used 15 gallons instead of 15000 gallons. From pool calculator for 15000 gallons, starting at 0 ppm FC, adding 48 ounces of dichlor, I get 13 ppm FC and a rise of 12 ppm CYA.:-D
Click to expand...
Whew! That is a good thing. I copied and pasted the 15,850 from the OP into the poolcalc, and while I did think that was kinda high for an FC value, I didn't go back and check.
 
linen said:
Yeah, the test strips tend to be useless. I would get a good test kit (see my sig).
Click to expand...
The only test kits that I have seen here is the HTH kit, which I have and it agrees with the test strips. It is however a fairly basic kit. I will do what you suggested and take a sample to a pool centre.
 
With a 15,000 gallon pool it would be worth the trouble and expense to get a good test kit. Since you quoted your volume in litres I'm going to assume you're not in the US so that makes it a little harder and more expensive to find a good kit. Look for a K-2006 if you're in Canada or a Palintest 315C elsewhere.
 
Dave, I'm in South Africa, and I havent actively gone looking for a good kit, but the only one that I have noticed in the stores is the HTH kit, which is a fairly basic kit.
By the way, my pool has now turned blue and is starting to clear up, without having put any more chemicals in. Maybe I should patent this "problem" :lol:

For the record, I phoned up a pool place that offers free water testing and asked how they test the water. They told me that they use a strip, so I didn't bother taking in a sample.
 

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Maybe the pool store can special order you a Taylor K-2006 kit?

Or, perhaps TFTestkits.net knows of a solution. I'd contact them and ask for advice. You can use the contact form/page on the website to send an email.
 
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