Free Chlorine Higher than Total Chlorine

[Darko5500]

Is it normal that FC is higher than TC? My test results are:

FC=5.3
TC=5.0
PH=7.4
CH=250
CY=100
TA= 100

I have just started to move away from pool shop measurements and adopted the BBB method as discussed in forums here.
I use a Milwaukee MI413 Photometer for the Chlorine check and a basic Taylor test kit for TA and PH. My CYA and CH is done via a strip test at my local pool shop, so reliability is questionable. I have only been a pool owner for 12 months but my pool is roughly 20 y.o.

Cheers,
D.

 

[BoDarville]

Is it normal that FC is higher than TC?

No. FC can only be equal to or less than TC. FC+CC=TC

 

[Patrick_B]

Welcome to the forum!

Not familiar with your machine, but that is a minor test error or variation. You should have a TC of 5.3 if there is no Combined Chlorine. What you don't want is your TC to be more than your FC by more than 0.5 Ideally.

Free + Combined= Total.

Your CYA is high at 100 and might be more than that. Not good, because it requires you to have a high FC level to be effective. See the links in my sig line and start reading the ABC's.

 

[Darko5500]

Thanks BoDarville. What do you suggest I do in regards to measurement? The photometer is brand new and seems far more accurate than my local pool shop. The basic Taylor kit I have also reads 5 for TC.

 

[Darko5500]

Thanks Brushpup, I will follow the links. I have been reading up on the some of the basic water testing procedures here and am looking to further my knowledge. I should mention that the photometer reads in mg/l which is nigh on the same as ppm.

I think the Cya is wrong anyway as I have drained some water from the pool and topped back up with fresh fill. This measurement was taken prior to the drain and the previous test at the same shop showed 80.

 

[Patrick_B]

Just curious, do you know the range capability of the photometer? Ones I am familiar with usually top out at 10 or less without sample dilution. I think 5 is the top end of that particular Taylor kit, but I stand to be corrected on that. If you can get Taylor stuff down under, you ought to get one of their FAS/DPD kits for FC.

You are correct about the mg/L conversion, yes.

 

[Darko5500]

This Milwaukee meter does top out at 10mg/l and the Taylor at 5. I am definitely keen to get a better Taylor test kit but one of the distributors down here has stopped importing them.

 

[Patrick_B]

You might still check with some to see if there are any left. I'm just not familiar with shipping stuff down there or I would have the perfect solution for you. We like TFtestkits.net, but you will have to ask them about overseas shipping. I presume lots of problems getting chems into another country, but I just don't know.

 

[BoDarville]

What do you suggest I do in regards to measurement?

Honestly, I'm not familiar with that testing instrument. If there is any way you can get a FAS-DPD chlorine test, I would suggest that.

CY=100

I'm assuming this is CYA. As you have already pointed out, I would also be suspect of the accuracy of the results since they came from pool store test strips. If you can get a CYA test that uses reagent R-0013, I would do so and then retest. If not, then your current results are all we have to go on. If that's the case, I would drain 50-60% of your pool water and refill as this is the only way to reduce CYA.

The chlorine / CYA relationship is a cornerstone of pool water management. Understanding this will help you avoid the majority of problems that plague many pool owners. Take a look at the Chlorine CYA Chart.

 

[Darko5500]

Thanks for all the tips. I did see that CYA chart which is what led me to submit this post. I will see if I can find a more reliable test for CYA and then repost. Might take a while to source though.

 

[Darko5500]

Hi Guys, finally managed to import a Taylor k2006 kit into Oz. here are my readings;

TA 90
pH 7.6
CH 260
CYA 80
FC 8.5
CC 0.5

My Martini Instruments Photometer shows FC 7.8 and TC 7.8.

Pretty happy with the overall results. Guess I need to drop the CYA level and then I'll be able to adjust the FC down a little.

Cheers,
D.

 

[Patrick_B]

Sounds like a plan to me. Not bad readings from the machine on FC. As for the CC number....not so sure about that one. Weird.

 

[Darko5500]

Thanks Brushpup. I'm getting more consistent readings with the photometer. It pretty much always shows the TC the same or slightly higher than the FC now. The first couple of weeks using it it always showed FC higher. Must have been inconsistent with my testing methodology.

 

[Patrick_B]

Sure thing......

Maybe it is method...something you are missing or not doing with the right timing. Photometers I have used, normally read FC immediately, and
the TC takes a 3 minute cook time before reading. Something seems amiss. Still, 7.8 FC compared to 8.5 titrating for FC ain't too shabby.

 

[Darko5500]

Agree it must be in the timing. The instructions say to wait 2mins 30sec.

 

[linen]

No need to drop the cya level since you are using a swg. Our recommended range is 70-80 ppm cya: http://www.troublefreepool.com/pool-school/water_balance_saltwater_generator

 

[Pittsburghtony]

I use a test strip and the standard liquid cl ph test on my in ground diving pool. The liquid test tell me that my ph and cl are both in the upper range of ideal, but my test strips say that the “total chlorine” is low while the “free chlorine” is ideal and that the stablizer and hardness are both on the low side. I know not to add too much chemical to raise the stablizer because that can lock the chlorine making it less effective, which I had done one year when I didn’t give it enough time to take effect and added more over the recommended dose. Anyway I’m seeing a lot of other people getting a higher free chlorine reading than the total chlorine reading as I am and I’m wondering if these so called experts who say that’s impossible really know what they’re talking about. I’ve been working with pools for over thirty years, only twenty one with this big of a pool and maintain the water crystal clear. Usually I do have some algae on the liner when opening the first time, which I vacuum scrub and shock. Once in a great while I do use a lid full of clarifier in the deep end to remove any slight cloudiness. Since two side of the area are surrounded by woods, I do have to net out leaves frequently and vacuum one to two times a week. I also use the 68% granulated chlorine to both maintain and shock the pool, with also some regular baking soda to raise the ph level when needed. I have tried the chlorine tabs in the past but they never worked for me. I’ve only had the pool professionally tested a few times, but don’t like that because they’re always try to sale me a lot of chemicals, saying I need it, which I knew some of those I did not, or could have used a lot less expensive alternative. In over these thirty years I have had many people swimming and no one has ever gotten sick, or even complained about too much chlorine.