Can High CC cause false FC positives with DPD test kit (K-2006C)?

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Ted2019

Ted2019

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May 10, 2019
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Lido Beach, NY
AquaChek claims that High CC will cause false FC positives with DPD test kit. They say that with high CC their test strips will show "0" FC while the DPD testing method will show a false positive? High CC happens to me every year upon opening --- only fix is to put in breakpoint dosage per Taylor's instructions (CC x 10 x factor for % Chlor & volume/ 16 oz bags since I use BioGuard Burnout 3).
My K-2006 test results are FC=1.0; CC= 5.0; Alk=120; PH =7.7; CYA<30.
The AquaChek results are: Total C=5.0 & FC = "0"; thus all Chlor is CC.

Both test would indicate that I need only 10 bags of 16oz Burnout 3 ( 5.0 x10=50 x 3.1 (from Taylor table) = 155 oz. divided by 16 = 10 bags)

My question is: will the Taylor kit give me the correct CC number if the FC number is a "false positive"? When I got samples tested at a pool store with BioGuard computer, they usually get a much higher CC --- thus conveniently needing more bags of Burnout 3.

My past experience with "Pool stores" always showed conflicting results --- that's why I got the K-2006C years ago. Never have a problem during the season but upon opening, I always get the high CC. My pool is covered with a Meyco solid cover but with drain screen in the middle of the cover. I do have trees around my pool and I live very close to the ocean.

Thanks for any advice.
 
:wave: Welcome to TFP!

We have a bit of a terminology problem here. A dpd chlorine test is not the same as an fas-dpd chlorine test. The former only reports total chlorine which would include CC, but the latter will not be hampered by any false results. Trust the K-2006 test results.

Beyond that, we would recommend greatly changing your opening procedure as the breakpoint chlorination is generally not realistic. And, in addition to that, there is certainly no need to use expensive BioGuard products.
 
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When a cover is used continuously, without routine opening to allow outgassing your testing can show more CCs than are really a problem. You should open the pool cover up ever few days to allow the sun to burn off some CCs and let the pool "breath" a bit.

Maddie :flower:
 
YippeeSkippy said:
When a cover is used continuously, without routine opening to allow outgassing your testing can show more CCs than are really a problem. You should open the pool cover up ever few days to allow the sun to burn off some CCs and let the pool "breath" a bit.

Maddie :flower:
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Thanks for the advice but it would be difficult since I have a "winter cover" (Long Island, NY) that would be difficult to regularly remove & replace. I do open a corner whenever rain or snowmelt causes an overflow. Your pool and yard look beautiful! See attached --- water weights are used to help block tree debris & beach sand from Pool 2019 winter.jpgDSC01025.JPGDSC01025.JPGDSC01025.JPGPool 2019 winter.jpg entering pool in winter.
 
jblizzle said:
:wave: Welcome to TFP!

We have a bit of a terminology problem here. A dpd chlorine test is not the same as an fas-dpd chlorine test. The former only reports total chlorine which would include CC, but the latter will not be hampered by any false results. Trust the K-2006 test results.

Beyond that, we would recommend greatly changing your opening procedure as the breakpoint chlorination is generally not realistic. And, in addition to that, there is certainly no need to use expensive BioGuard products.
Click to expand...
Thanks for the response.....so since the K-2006 is a fas-dpd, it's results s/b good. I was just concerned that since the first part of the K-2006 test is only for FC, that if it gave a false positive, it might skew the second part of the test for CC.

Not sure I know what you mean by "changing the opening procedure as the breakpoint chlorination is generally not realistic"? What's a cheaper alternative to Burnout 3 --- assume any 58%-60% Calcium Hypo?

Thanks again!
 
In the winter, obviously you would not need to remove the cover.
But, when you open, you might consider removing the cover for a few days before you start to balance it to let some of the CC burn off.
Breakpoint chlorination is a fallacy. It is only remotely correct if the CC reading is due to a specific reason.
You would be better off performing a full set of test results to get a full picture of the water ... for example, if your CYA dropped to 0 over the winter and you had a high CC level, that would point to a different issue than if the CYA was still there.
To remove the CC, you should just follow the SLAM Process process which is very specific about the amount of chlorine you are adding to not put your pool at risk.
Do you need to add calcium to your pool? If not, then why use cal-hypo at all? We would recommend just using liquid chlorine as there are no side-effects like the solid forms of chlorine.
 
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Ted,

Welcome to TFP! As you can see from Jason's comments we use different methodology that is based on simple methods that are based on sound science and very easy to perform so anybody can successfully use it. We start with owner performed tests. Please post a full set of results. FC, CC, pH, TA, CH plus salt, Borates if you use them. As Jason has recommended a SLAM will quickly fully oxidize your cc. He's one of our experts that will get through the start up and on the way to cheap easy trouble free sparkling pool. Just ask any questions and you'll pick this up very quickly. Here are a couple of links that may he helpful:
Pool School
Pool School

Basic Pool Care Schedule
Basic Pool Care Schedule

Temporary Pool Guide
Temporary Pool Guide

Pool Definitions and Abbreviations
Pool Definitions and Abbreviations

ABC's of Pool Water Chemistry
ABC's of Pool Water Chemistry

Recommended Pool Chemicals
Recommended Pool Chemicals

How to Chlorinate Your Pool
How to Chlorinate Your Pool

Chlorine CYA Chart
Chlorine CYA Chart
 
Never thought about when opening, to wait a few days to start balancing --- good idea! Thanks!

Based on your reply, I re-checked my CYA with the K-2006 and it seems to be much lower than 30 since I could still see the dot at the top reading of 30. My Aqua Chek strip also showed it to be "lower than 30" --- it could be "0". During the season, I use both a stabilized chlorine (tabs) and non-stabilized chlorine (shock) since the stabilized chlorine increases the CYA too much. Upon opening, the CYA is usually between 0 and 30. So I do have very low CYA and high CC?

I also rechecked the FC and CC and got .4 and 6.4 respectively.
 

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With that CC and you do not have low pH, I would suggest following the ammonia protocol prior to adding CYA.
To check and defeat ammonia, if necessary, is to raise your FC in the water using enough liquid chlorine to get to 10 ppm using PoolMath. Circulate the pool for 15 minutes. Test FC. If at 5 or below, add LC to get to 10 using LC, circulate for 15 minutes, repeat until your FC is above 5 ppm after the 15 minute circulation is above 5 ppm.
 
mknauss said:
With that CC and you do not have low pH, I would suggest following the ammonia protocol prior to adding CYA.
To check and defeat ammonia, if necessary, is to raise your FC in the water using enough liquid chlorine to get to 10 ppm using PoolMath. Circulate the pool for 15 minutes. Test FC. If at 5 or below, add LC to get to 10 using LC, circulate for 15 minutes, repeat until your FC is above 5 ppm after the 15 minute circulation is above 5 ppm.
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Good catch Marty! Could be something added had ammonia in it previously or something "under the cover" added ammonia. Either way the ammonia protocol is easily transitioned to a SLAM which is the next choice after eliminating ammonia.

Good luck Ted you've got the best of the best with Marty and Jason!

Chris
 
You got it, and you will certainly need more than just the 1 gallon. If you can reliably test and dose every 15 minutes or so, you should be able to get rid of the ammonia in a few hours and then follow the SLAM Process process.

Some people like to get an ammonia test (pet store ... or have them do the ammonia test) to see how high the level really is. Given that level, there is a way to estimate how much FC would be needed to eradicate the ammonia (and CCs) (this is kind of sort of like the breakpoint method you mentioned, but it is not based on the CC level, it is based on the ammonia level and know how much CC will be generated as the ammonia is broken down).

You could have a boat load of ammonia in the water and 0 FC and 0 CC. The CC will not start to show up until you add FC to react with the ammonia. So as you can see there is no way to know how much FC will be needed just based on the CC level.
 
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