Free Chlorine test and pH meter

[jiangu1]

I just received my tftestkit-100, and measured free chlorine level. I expected to see water change back to clear after I added the last chemical, but the color still changed from red to a dark hue clear at drop 50, and remained that way at drop 60. Will the solution ever go to completely clear? See attached photo.

I also received my pH meter. Anyone knows if the meter was calibrated before shipping?

Thank you!

 

[HermanTX]

Seems strange. Just want to make sure you followed the correct process for test Free Chlorine (FC). In the 10ml sample, once you add the R0870 powder it should turn pink. Then count drops by adding R0871 for it to turn clear. It is pretty obvious when the solution turns clear. It becomes a very light pink as you add drops then clear on next 1 or 2 drops. Do not add R-0003 drops until after the solution turns clear.

I cannot comment on pH meter as I do not have one.

 

[cme4oil]

Check the reagents you are using. Sounds like you might have used the wrong one(s).

 

[jiangu1]

Thanks for both your replies! I used right chemical, but last photo may have 0003 in it.

I tried again tonight without any 0003. I saw a problem of color changing from clear to pink if I waited sometime. Here are some photos: 1) just 0870, 2) 30 drops 0871, 3) 36 drops (clear), 4) wait 1 min, went back to pink. After I added one more drop, it became clear, but the pink again. I kept doing this until 49 drops. Then I waited 1 hour (photo 5). Then added until drop 60 and cannot make it clear (photo 6). I feel i couldn't do accurate FC test. Help!

 

[aussieta]

do not wait on the fc test
1 drop per second
when it turns clear that is it
if you leave sample it will always go pink again. false positive

 

[Wobblerlorri]

The pH meter is not calibrated when you receive it. You have to mix up the standards in 250 mL of distilled water each and calibrate it yourself per the instructions. Be sure to calibrate the meter at least once a month, more often if it starts acting up.

As for the FC test, add drops until it goes clear, then stop. You're done. That's your FC amt after multiplying by 0.5 or 0.2, depending on your sample size. (Use 10 mL, your reagents will last longer.) Then add 5 drops of R-0003 for the CC test, and titrate only if it turns pink. If it stays clear, you have 0 CC.

 

[duraleigh]

The FC sample pic seems to show about 12-13 ml water in the tube. Why is that? It should be 10 ml.

This test is a simple short test. Count the drops until it goes clear and then stop.....the test is done.

Do you have an idea of how much chlorine is in your pool? Have you tried the OTO test (The one that turns yellow)?

 

[HermanTX]

As noted by others, once the solution turns clear then that is it. So in your test example needing 36 drops. Dividing by 2 gives a FC of 18. This seems very high. Now this could be influenced by your test sample volume. It should be a level 10ml - not 9, not 11 or 12. It takes some practice but try to get a consistent 10ml sample. Be sure to rinse it first to remove any remnants of previous test. Then once it turns clear note the number of drops then add 5 drops of R-0003. If it stays clear there are no CC. If it does turn a light pink, adding 1 or 2 drops of R-0871 again should turn it back to clear. Test over. Then rinse out and go on to next test. Good Luck.

 

[jiangu1]

Thanks for all your replies! I will do the test quick without wait then. I was SLAMing the pool and my pool's CYA is high (60 ppm). That's why FC level was so high a few days after SLAMing. I used 10 ml sample, and the drops (>36) made the volume higher.

I will calibrate the pH meter. The instruction is quite minimum. Can the calibration solution be stored for repeated calibration? I would appreciate if bottles were provided. Anyway, the reason I want to use the pH meter is that I saw people mentioned that phenol red pH measurement is not accurate during SLAMing. For which chlorine level can I use the phenol red for pH?

 

[setsailsoon]

Thanks for all your replies! I will do the test quick without wait then. I was SLAMing the pool and my pool's CYA is high (60 ppm). That's why FC level was so high a few days after SLAMing. I used 10 ml sample, and the drops (>36) made the volume higher.

I will calibrate the pH meter. The instruction is quite minimum. Can the calibration solution be stored for repeated calibration? I would appreciate if bottles were provided. Anyway, the reason I want to use the pH meter is that I saw people mentioned that phenol red pH measurement is not accurate during SLAMing. For which chlorine level can I use the phenol red for pH?

Jian,

In normal use I have a small 2 oz Nalgene container that I use to store calibration fluid. It's like the one pictured below. These work well because they seal from evaporation and have enough weight that they hold the pH probe from tipping over. I replace the calibration fluid every week to 10 days and I store it inside the house. The amount of time it lasts depends on storage conditions and frequency of use. Each time you use there is a drop or two of contamination. Be sure to shake the liquid from the tip before you use it. Also be sure the tip does not dry out. FC above 10 causes the phenol test to be unreliable.

As many have indicated do the FC test rapidly add drops then swirl then more until clear. First time it is clear is your result. If you wait it will always turn red again.

I hope this is helpful.

Chris

 

[duraleigh]

I want to use the pH meter is that I saw people mentioned that phenol red pH measurement is not accurate during SLAMing.

The pH meter is liked by many members. However, there is NO REASON to check pH during the SLAM so don't buy a pH meter just for that purpose.

 

[setsailsoon]

Jian,

Dave's right. I should have mentioned that. I only use the pH probe because I have difficulty discerning the orange-red-purple range (hereditary male color-blind). If you're not color-blind like me there's really no need for the digital tester and pH during a SLAM is not needed. (thanks Dave)

Chris

 

[jiangu1]

Chris and Dave, thank you for your inputs! That makes me much comfortable about pH measurement. I will wait FC to go down and then test the pH using color.

Regarding waiting and solution will turn red, will this affect the CC measurement, e.g. after adding R0003, the solution will turn red not because of CC but because of the delayed time? wondering what is the chemistry behind it.

Jian

 

[Brett S]

The FC sample pic seems to show about 12-13 ml water in the tube. Why is that? It should be 10 ml.

I think it’s because of the number of drops that were added. If you look at the first pink with the very dark pink sample that seems pretty closed to 10ml by the time you account for the meniscus. But after 30 or 40 or 60 drops I’m sure it could add another ml or two of liquid.