Combined Chlorine Problem-help!

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T

TazJMT

0
Jun 19, 2014
111
Spotswood, NJ
Hello All,

Sorry this is so long, want to be very detailed.

(10,000 gal above ground pool sand filter and vinyl liner)

Having issues need help. I opened my pool 5 days ago (late this year because it wouldn't stop raining for most of June here in NJ). Normally I start by adding some algaecide and a pound or 2 of Cal-Hypo (depending on what the water looks like when I open it). When I close it, I get the chlorine level near zero (so it doesnt eat my cover and now I can finally get a few seasons out of a cover). Usually opens up great.

This year, water opened a little cloudy and the cover looked porous in some spots, so I threw it out (maybe some organic material from leaves made it into the pool?). We were also down about a foot of water, so I am assuming when it rained and the cover was weighed down, some water from the pool came through and got lost when I pumped the water off the top of the cover periodically. After a day of running the pump, I was getting a FC level of near zero. I've had that before, figured some algae I couldnt see was using up the chlorine, so I added another bag of shock. Next day, still no FC. Did that one more time and still 0 FC, so I decided to finally take a trip the the pool store nearby and get a better test done (and because of the results I will show next, I actually went to a 2nd shop to confirm).

Though they didn't agree on the numbers, both shops both showed that I had a high combined chlorine level and described it as "chlorine lock". My research here shows me we don't like that term, but that's what they said. This was the results:

TC 6.2
FC 0.1
ph 7.4
TA 130
CH 150
CYA 0

The CYA being 0 is super weird for me, every year I am biting my nails to see if it will stay under 85 by the end of the season-last Sept I closed it with 85 CYA.

So they did some math and told me I would need 12 pounds of non chlorine oxidizing shock to solve the issue-I actually used 14 pounds since they had a 10lb and 4lb container.
I added it to the water all in one batch (using a plastic cup about 1/2 lb at a time) and ran the pump for 48 hours straight-it has been mid 90's and sunny out
I also took all my tri-chlor pucks out because some research tells me I don't want to add the small amount of chlorine in a couple pucks before the issue is solved as it could just convert right to combined-hopefully that is right

Took it back to the store today and obviously no good, hence the post. Here are the results:
TC 4.9
FC 0.0
ph 7.1
TA 135
CH 100
CYA 0

I backwashed after running the pump 48 hours and it came out like milk for about 15 seconds before clearing up

They suggested I add 1 bag of Cal-hypo and run the pump for 2 hours just to see if it registers any FC at all (kind of a test?). I didn't understand that exercise but i did it. It did not give me any FC, so I called him to let him know. He told me he will get back to me tomorrow-hoping that doesnt make the TC/CC problem worse

I thought the oxidizer would work, but my only concern there is that the other store I went to did a test with a sample from the same bottle within 20 mins of each other and had results of TC=11.5 and TC=1.1 (and all other levels similar)-I think the math says that would have required 20lbs of oxidizer. The reason I didn't go with them is they told me to add oxidizer 2 lbs at a time every 12 hours, which made no sense to me.

Both stores show a problem, but differ on the degrees. The store that showed 6.2 and 4.9 TC dips a strip in the water, and then that strip is inserted into a computer. The other store uses a syringe looking thing to inject water into the puck looking thing, which is then also inserted into a computer.

I am very frustrated as it has been hot and we want to use the pool. I assume algae is coming any day now since I have not been adding any chlorine to the pool. Can anyone help me?
 
There seems to be a lot of signs that your cya converted to ammonia thus the rapid FC loss and high cc's. Please stop going to the pool store and adding everything they tell you to :) do you have one of the recommended test kit so that we can help you get this straightened out?
 
Oh wait I just realized that that 14 lb that you threw in the pool initially was non-chlorine shock. That will show up as CC in the tests. You've created quite the chemical soup right now :) the question still stands whether you have the proper test kit for us to get to the bottom of this. We just do not trust Pool Store testing at all
 
I agree with what Jason suspects is ammonia. I just want to mention that stabilizer CYA feeds and creates more ammonia. So do not add any chemicals like trichlor pucks or shock that add CYA until you get things sorted out.
 
jblizzle said:
Oh wait I just realized that that 14 lb that you threw in the pool initially was non-chlorine shock. That will show up as CC in the tests. You've created quite the chemical soup right now :) the question still stands whether you have the proper test kit for us to get to the bottom of this. We just do not trust Pool Store testing at all
Click to expand...
Yes now I see why. I do not have a "good" test kit but will order one tonight (in the meantime until it arrives my pool is just going to marinate i guess)

Is there one on the list you recommend over the others? I like both TFT test kits, but feel like i would run out of the CYA tests quickly as there are only 15 of them
 
You only need to check CYA once every month or two once you get it to the desired level.

The TF-100 Test Kits should last you a year or more before you need refills.
 
TFTestkits.net ships from NC. If they ship on Monday you should get it Weds-Thurs.

The site says

USPS Express Mail is available if you need next day delivery as is UPS 2-Day Delivery or Overnight
 

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Once you get the test kit, you'll be ready to SLAM. You should get the necessary liquid chlorine to begin. You can bring the chlorine up to about 15 now to get a head start.

Don't add any more nonchlorine shock.
 
ajw22 said:
I agree with what Jason suspects is ammonia. I just want to mention that stabilizer CYA feeds and creates more ammonia. So do not add any chemicals like trichlor pucks or shock that add CYA until you get things sorted out.
Click to expand...
See this reply
 
Basically there’s a bacteria that eats CYA and makes ammonia. Adding chlorine will cause the ammonia to be cancelled but will also eat the chlorine and make CCs instead. You have to keep feeding in chlorine and testing often (so you don’t add too much chlorine) until you break through the ammonia and get the bacteria. Then once you’re holding FC and know you’re done with the bacteria you can add CYA.
 
You can use poolmath to calculate the amount of liquid chlorine. I would start with about a gallon of liquid chlorine.

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.
www.troublefreepool.com

Most likely, you have bacteria in the water that ate the CYA and converted it into ammonia. You need to kill the bacteria first before adding CYA.

Oxidizing ammonia is acidic, so the pH and TA will drop as you add liquid chlorine. That's one indication of ammonia.

The missing CYA and high CCs are a good indication of ammonia.

The bacteria are killed by chlorine pretty easily. Once you're holding an fc level, you can add some CYA.
 
Last edited:
IceShadow said:
Basically there’s a bacteria that eats CYA and makes ammonia. Adding chlorine will cause the ammonia to be cancelled but will also eat the chlorine and make CCs instead. You have to keep feeding in chlorine and testing often (so you don’t add too much chlorine) until you break through the ammonia and get the bacteria. Then once you’re holding FC and know you’re done with the bacteria you can add CYA.
Click to expand...
Ah that makes sense, thanks. If I have no CYA (because of that), wouldn't the sun destroy the chlorine added before it can do its job?
 

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