Chlorine Test Results

[planoattorney]

I converted to the BBB method this year and got my own Test Kit which makes me as happy as a 14 year old boy with a junior chemistry set and a poster of Kelly LaBrock.

However, I am having confusing readings and need help figuring out what I am doing wrong. Using the small blue box (the daily test) my chlorine is off the chart. 5 drops of reagent makes the sample more yellow than the color codes on the vile. Test strips give similar results. But if I do the DPD test, chlorine is checking in between 2 and 4 (always well within the color codes for the R-0600 test). I have tried this several times, I keep getting the same result, the DPD test shows less than half the chlorine the R-0600 test shows. I generally add one quart of 12.5% bleach which according to the Pool Math Calculator would raise my FC by more than 3 PPM. Just to test my concerns, I added 2 quarts of bleach, waited a couple hours and did a DPD test which showed FC of only 5, while the R-0600 test went off the charts around 3 drops - either way the amount of chlorine I added should have raised the FC to well over what the DPD test showed. I added the chlorine in late evening so it was not burned off by the sun.

I was storing my test kit in the cabinet in the garage. It gets hot, probably up in the 90's on the hottest days, but it is dry and out of sunlight. Can the heat in the garage kill my reagents? Any suggestions? Should I repeat the test and use extra DPD powder (is it possible I am not using enough? That scoop picks up about half a B-B in volume, it is tiny - am I supposed to be scooping using the flat side?)

This morning's test results are:

FC = ??? Per R-0600 >5, per DPD - 3.5
CC = 0
Ph = 7.2
TA = 50
CH = 350
CYA = 40
Water temp = 87F
Borax = >50

I know the TA is low right now, it and the Ph were high yesterday so I added acid (lots) and a box of borax to get that back up to >50, then ran the pump all night.

The water is crystal and I just want to keep it that way.

 

[mknauss]

I will take a shot at answering a few of your questions.

The strips and the OTO are not very accurate. We say the strips are guess strips and the OTO is an indicator you have chlorine.

The test kit should be kept in a cool, dark place. I keep mine in our laundry room cabinet. I would not keep it in a garage or shed in Texas.

When you do the FAS-DPD, you do need to use enough powder. Use the scoop end. There should be a speck or two of the powder that does NOT dissolve in the sample you are testing after adding the powder. If you are unsure, add a bit more powder. It is cheap.

Your TA of 50 is fine if you pH stabilized there. Borax doe not have a great effect on TA, but does raise your pH, which when you then drop it, reduces your TA. I would suggest doing your best to not get into a yo-yo effect on pH and TA. Only add acid if your pH goes above 7.8. Then only enough acid to drop pH to 7.5. Hopefully then the TA and pH will stablize.

 

[Rollercoastr]

I converted to the BBB method this year and got my own Test Kit which makes me as happy as a 14 year old boy with a junior chemistry set and a poster of Kelly LaBrock.

We must be about the same age... "What do you little maniacs want to do furhhhst?"

 

[slickraft]

First, I agree with others. Only use FAS DPD chlorine tests for meaningful numbers.

Second, your stats say you have a 14K pool. When I check Pool Math it says 32 oz of 12.5% bleach will raise FC by 2.2 ppm on your size pool. You say you tested this by adding 2 quarts of 12.5% and the test showed an increase of only 5 ppm. I'd say that is right on the money. Are you inputting the numbers correctly into Pool Math?

In this video they show how to use the scoop while doing the CL test but I think your TF-100 testing is fine but maybe you have a Pool Math error.
FAS/DPD Chlorine test for the TF-100 - YouTube

 

[planoattorney]

We must be about the same age... "What do you little maniacs want to do furhhhst?"

I was not sure it the reference would be lost, glad to know at least one other member got it. My wife is younger than me and had no clue. I am clueless, but figured going on-line to buy a Kelly LaBrock poster may cross some line, but I should probably find the movie.

- - - Updated - - -

First, I agree with others. Only use FAS DPD chlorine tests for meaningful numbers.

Second, your stats say you have a 14K pool. When I check Pool Math it says 32 oz of 12.5% bleach will raise FC by 2.2 ppm on your size pool. You say you tested this by adding 2 quarts of 12.5% and the test showed an increase of only 5 ppm. I'd say that is right on the money. Are you inputting the numbers correctly into Pool Math?

In this video they show how to use the scoop while doing the CL test but I think your TF-100 testing is fine but maybe you have a Pool Math error.
FAS/DPD Chlorine test for the TF-100 - YouTube

Operator error could be at the center of the debate - it is the lowest common denominator and I was not using a "heaping scoop" though with that little amount, "heaping" could be a matter of interpretation. The test water goes bright pink, I figured that meant there was enough powder,

Do most people here just forgo the R-0600 test altogether? If it is not trustworthy, how about the Ph test in that same kit? Is it trustworthy? Is there a better test for Ph that I can use with the rest of my TF-100 kit?

 

[mknauss]

The OTO pH test is very accurate with FC less than 10. The OTO TC test, not so much. It is an indicator, is the TC low or high?

I use my OTO TC test in the winter. When I just want to be sure I have chlorine in the water.

Take care.