What to Do if Biguinide Color on Test Strip Is Blue

thetinkerer

I tested my FC and found it to be 3 but my Total Chlorine is high meaning my Combined Chlorine is high? I used my Basic Kit for a Total Chlorine reading and found it to be dark yellow. I also noticed the "chlorine smell" a few nights before...

I figure my Combined Chlorine is the culpret so I shocked last night with two 1 pound bags of Sodium Hypochlorite (the pool is 8700 gallons) and let the pump run until morning. I tested the water again this morning and the Total Chlorine is still that dark yellow color.

Here are the numbers:
FC= 3
Total Chlorine = dark yellow
PH=7.5
TA= 100
CH = 250

I am not sure what is going on and why I am getting / keep getting the dark yellow readings on my total Chlorine.

Please help!

Thank you in advance..

thetinkerer..

Bama Rambler

Do you have a FAS-DPD test? If not, what are you using to test FC?

Your problem is that you aren't shocking the pool. Throwing a couple of bags in it isn't shocking.

JohnT

What is your CYA level, and what test are you using for TC and FC?

JasonLion

The OTO chlorine test turns a particularly vivid yellow when the TC level is between 5 and 15, light orange is between 10 and 20, dark orange is between 15 and 30, and brown is 30 or higher.

thetinkerer

I am using my TF-100 test kit that tests FAS/DPD. I use my Taylor BASIC kit to test for TC . My CYA is 50.

If shocking is my problem then how do I know how much shock treatment to use....what are the guidelines....

Thanks again so much!

Bama Rambler

Since you have a FAS-DPD test, it's easy to give us a CC result.

thetinkerer

CC looks like it is around 13 ppm so 3 for the FC and 10 for the CC. But for future reference how do I know how many lbs of shock to use based on these numbers?

Bama Rambler

If you have cc's of 10 ppm you seriously need to perform the shock process.

What we recommend to use to bring the pool the shock level doesn't come in lbs. It comes in ozs and gallons. Liquid chlorine or bleach.

You use the pool calculator to figure out how much you need to get from where you are to where you need to be based on your CYA level.

thetinkerer

But the pool calculator does not have an entry for CC just FC so how do I use to to determine how many gallons of chlorine to put in - I need to learn this ...
could you give me the numbers

entries are
FC - so mine is say 3
PH - mine is 7.5
TA - mine is 100
CH - mine is 250
CYA - mine is 50

what am i missing - how does this work??

thetinkerer

or walk me thru on how I would use the pool calculator to determine the no. of gallons to put in...

thanks again

linen

Total chlorine (TC) = Free chlorine (FC) + combined chlorine (CC).

FC is the good stuff and you use the pool calculator calculate how much chlorine to add to raise that level. CC is kind of the bad stuff since it indicates that your pool is breaking down something. You will want to see the CC number go down during the shocking process. We don't really care about TC.

The FAS-DPD test tests FC first, then the second part of the test is for CC (when you add the R-0003). What was your CC result...10 or 13 ppm?

As Bama said, either way you will want to do the shocking process since CC is above 0.5 ppm.

Using poolcalculator.com, for your 8700 gallon pool, cya of 50 ppm, it gives me a FC shock level of 16 ppm. Using those numbers it says you need to add 235 ounces of 6% bleach to raise you pool from 3 ppm to 16 ppm.

thetinkerer

Where or how did you get an FC shock level of 16 ppm? You say "it gives me a FC shock level of 16 ppm but not sure how it gives you that number......Did you add FC(3)+CC(13) = TC of 16? and use that in the pool calculator for "TARGET" and use 3 for "NOW" to get 235 oz?
Could you send me a screen shot if that helps
Thanks again....!!

chiefwej

It sounds like you need to read the test directions more carefully. This is from the extended test directions. It doesn't sound like you are doing the test correctly. It gives you FC, CC, and TC from the results of one test. It requires no color matching because it is a titration test where you just count the drops until color changes.

FAS-DPD Chlorine Test
FC and CC - Free Chlorine and Combined Chlorine

Rinse the sample tube with pool water.
Fill the sample tube with pool water to the 10 ml mark. The top of the sample will be curved. This curve is called a meniscus. The bottom of the meniscus should be level with the 10 ml mark.
Using the small spoon shaped end of the dipper, add one heaping dipper, or two level dippers, of R-0870 and swirl to mix. If the sample turns pink for a moment and then turns clear again, or if it turns brown, add another dipper of R-0870. If the sample remains clear the entire time, your FC level is probably zero, however it is best to verify that with an OTO chlorine test, since the FAS-DPD test is prone to the occasional false zero.
Swirling constantly and counting the number of drops as you go, add R-0871 one drop at a time. Continue adding drops until the color changes to clear. The pink color may become extremely faint before it goes away. Make sure that the sample goes completely clear.
Multiply the number of drops by 0.5 to get your FC level.
Add 5 drops of R-0003 and swirl to mix. If the sample remains clear, your CC level is zero.
If the sample turns pink again, add R-0871 one drop at a time, swirling constantly and counting the number of drops as you go. Continue adding drops until the color changes to clear. The pink color may become extremely faint before it goes away. Make sure that the sample goes completely clear.
Multiply the number of drops by 0.5 to get your CC level.
Dispose of the sample safely. It is best to pour it down the drain with the water running. Do not add it back to the pool.
Rinse the sample tube with tap water and store for next time.

Notes
Hold the dropper bottles vertically and squeeze gently, so that drops come out slowly and seem to hang on the tip of the dropper bottle for a moment before falling.
The exact amount of R-0870 powder used is not critical. The goal is to add more than you really need rather than using too little. Using too little R-0870 powder can throw off the results of the test. You need to use enough to bind to all of the chlorine that is present. Adding extra, within reason, has no effect. At very high FC levels it is likely that you will need to use more than the normal amount.
If left sitting on the counter, the sample will turn pink again one or two minutes after the test is completed. This is normal.
When measuring high FC levels, or measuring FC when the CC level is relatively high, it is important to move through the test quickly. Drops should be added about once per second, or slightly faster, swirling the entire time. You can slow down a little at the end of the test, to give you time to watch for the end point.
Over time, it is common for a cloudy residue to build up on sample tubes used for FAS-DPD chlorine testing. The residue can be removed by filling the sample tube with bleach, letting it sit for several minutes, rinsing, and then wiping throughly with a paper towel.
There isn't normally any reason to do this, but if you need more precision you can do this test with a 25 ml sample of pool water and multiply the number of drops by 0.2. In most situations the added precision is useless and simply wastes reagent.
R-0870 is DPD powder. The indicator in the powder turns pink when bound to chlorine. R-0870 powder gets darker over time and eventually starts to clump up. If it is clumped up, you should crush it back into a slightly lumpy powder before using it.
R-0871 is FAS-DPD titrating reagent. It should be a clear colorless liquid. If it turns a dark yellow color, it has gone bad.
R-0003 is DPD Reagent #3. It should be a clear colorless liquid. If it turns yellow, it has gone bad.
The precision of the measurement is plus or minus one drop when up to 10 drops of titrant are used, or plus or minus 10% of the final reading, when more than 10 drops of titrant are used."

Thinkly

First of all in relation to the pool calculator: The pool calculator tells you how much of something to put in based on your current test results, pool volume and desired results. You need to learn how to test for CC. CC is the "bad" stuff in your pool. Any reading over .5 and you have to "shock" your pool. Once you know that you have CC you can basically forget the CC number in terms of using the calculator, the important thing is that you have learned that you need to shock.

The pool calculator will tell you what the shock reading is supposed to be for your pool size and cya. In other words it will tell you that your FC reading needs to be 15 to reach shock level (for example.) So if you need to raise your FC to 15, you simply put your current FC reading into the calculator and put 15 for the desired reading and it will tell you how much to add.

linen

Looks like others have responded....here is my take:

Where or how did you get an FC shock level of 16 ppm?

From the "Suggested FC levels" section near the bottom of the table. The FC shocking level is listed there, you will need to put in your cya value into the now column to get the right suggested FC levels. Then I put 16 ppm into the target column in the FC section. CC is not used with the poolcalculator.

thetinkerer

ok I think I've got it thanks to all of your help.....one last question...how do I add the liquid chlorine to the pool water and do I add it once only or will I have to repeat - i guess that depends on whether my CC drops to .5 or below...after the first application...

linen

Add bleach/Liquid chlorine directly into pool in front a return so it is mixed quickly into the bulk of the pool water.

You will have to add it a number of times since the shocking process requires you keep your FC at your shock level. If you can test every hour, do that and redose chlorine.

thetinkerer

so if I check it every hour then what you are saying is that I will notice it clear up (get rid of the CCs) within an hour's period of time after enough re-dose appliations have been done....

linen

It is hard to say what the CC level will do, it may go down quickly or may take awhile. The shocking process has three criteria to know when you are done (they are also in my sig in red). You are not done with the shocking process until you pass all three simultaneously. The most important thing is to keep your FC at the shock level. Usually CC will go away long before you pass the Overnight Chlorine Loss Test (OCLT).

Lawson Loore1983

What to Do if Biguinide Color on Test Strip Is Blue

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