Which test kit for testing chlorine?

[anewbie]

I'm setting up an automated system which remove chlorine and i would like to be able to verify the water is 'fish' safe. My understanding is something over 1 billionth ppm is harmful - which test kit is cost effective for this application ?

[Drew O]

The Aquarium Coop multi test strips can measure chlorine.

 

[dasaltemelosguy]

@anewbie, These are a little pricey initially but not so much in the long run. They cost about 40c/test. The precision is terrific at 0.01ppm. 

 

Free Chlorine Colorimeter - Checker® HC

[anewbie]

On 5/19/2023 at 12:06 PM, dasaltemelosguy said:

@anewbie, These are a little pricey initially but not so much in the long run. They cost about 40c/test. The precision is terrific at 0.01ppm. 

 

Free Chlorine Colorimeter - Checker® HC

Yea - i've actually been looking at the 741 which is more accurate and a little less per test; but wasn't sure that is the route to go. Why would you pick the 701 over the 741 ?

[dasaltemelosguy]

On 5/19/2023 at 12:10 PM, anewbie said:

Yea - i've actually been looking at the 741 which is more accurate and a little less per test; but wasn't sure that is the route to go. Why would you pick the 701 over the 741 ?

I haven't been able to find the 741. Is it possible that it's an older model and has been replaced by this one (the 762)?

Ultra Low Range Free Chlorine Colorimeter – Checker® HC (hannainst.com)

I only see the 701 and the 762 on their website. Between these two, the 762 might be overkill as it's graduated in PPB vs PPM.

So, converting both to PPM, the 762 will read between 0.001PPM which seems unnecessarily low and only reads up to a maximum of 0.5PPM.

Whereas the 701 will read from 0.01PPM up to 2.5PPM which seems more in the useful range for aquariums. Municiple water supplies can read as high as 4PPM so I think the 701 is a more useful range unless you have specific plans and wish to monitor the chlorine at an extremely granular level. 

Here's the 701: Free Chlorine Colorimeter – Checker® HC HI701 (hannainst.com)

If I've missed the 741 somewhere, send me a link and I'm happy to look at it. I hope this helps.

 

[anewbie]

On 5/19/2023 at 4:50 PM, dasaltemelosguy said:

I haven't been able to find the 741. Is it possible that it's an older model and has been replaced by this one (the 762)?

Ultra Low Range Free Chlorine Colorimeter – Checker® HC (hannainst.com)

I only see the 701 and the 762 on their website. Between these two, the 762 might be overkill as it's graduated in PPB vs PPM.

So, converting both to PPM, the 762 will read between 0.001PPM which seems unnecessarily low and only reads up to a maximum of 0.5PPM.

Whereas the 701 will read from 0.01PPM up to 2.5PPM which seems more in the useful range for aquariums. Municiple water supplies can read as high as 4PPM so I think the 701 is a more useful range unless you have specific plans and wish to monitor the chlorine at an extremely granular level. 

Here's the 701: Free Chlorine Colorimeter – Checker® HC HI701 (hannainst.com)

If I've missed the 741 somewhere, send me a link and I'm happy to look at it. I hope this helps.

 

I typo'ed the number it is 761; the 761 measure total chlorine 1ppb; the 762 only measures free chlorine 1ppb; the 701 is ppm. So when i wrote 741 i meant 761 which you should now be able to find.

 

The 761 is $7 more for the kit; but (here is the kicker) the actual tests are less expensive than the 701 ($9 for 25 vs $10 - ok small difference).

 

Does that help. So my question is there any reason to not buy the 761 vs the 701.

[dasaltemelosguy]

Oh OK. It looks like the 762 has replaced the 761 but they seem to be very similar. In particular, the 761 has the same extremely low range, 0.001PPM to 0.5PPM. So, the above on the 762 applies to the 761 as well. It seems too granular to me, but you may have specific needs for such granularity. If you need 0.001 levels of accuracy and don't mind it topping out at 0.5PPM, then the 761 is a good choice.

Our Los Angeles water is 3PPM-4PPM out of the faucet so I'm guessing but chances are you won't be able to measure the chlorine of your water before any reduction as it's probably over 0.5PPM out of the faucet. 

[anewbie]

On 5/19/2023 at 5:03 PM, dasaltemelosguy said:

Oh OK. It looks like the 762 has replaced the 761 but they seem to be very similar. In particular, the 761 has the same extremely low range, 0.001PPM to 0.5PPM. So, the above on the 762 applies to the 761 as well. It seems too granular to me, but you may have specific needs for such granularity. If you need 0.001 levels of accuracy and don't mind it topping out at 0.5PPM, then the 761 is a good choice.

Our Los Angeles water is 3PPM-4PPM out of the faucet so I'm guessing but chances are you won't be able to measure the chlorine of your water before any reduction as it's probably over 0.5PPM out of the faucet. 

No - they are two different products both active. I asked them this morning about it - 761 measures all chlorine - 762 only measures 'free' chlorine if that makes sense to you. She highly recommended the 761 over the 762. btw tests for the 762 is 2.5 x more expensive ($1 each vs $0.36 for the 761).

-

Yea - so that is an interesting question - what happens if the chlorine is out of range - the answer is it shows the max value (500) but it blinks so you know it is out of range. Is that a bad thing for our application? My gut sez no but perhaps your gut sez otherwise ?

[dasaltemelosguy]

OK. Then I guess it's all about the upper range and if that's good enough for your purposes. Maybe so as you won't want 0.5PPM around anyway. 

But Free is more important to know than Total. Total chlorine is similar to the ammonia tests that include ammonium.

A Total Chlorine test combines the free chlorine and any chlorine compounds it created while disinfecting or reacting with the water. These compounds may not be harmful, or they may be. It's just like the ammonia tests when you could read a high value but it's not ammonia but rather, ammonium. It reads high but you can't tell which form of ammonia you've tested. So, Total doesn't tell you much about chlorine as a dangerous compound. Total tends to be more about swimming pools. 

Free chlorine is the active disinfectant that is not 'used up' yet. So Total is considered less useful and may be inaccurate insofar as testing chlorine levels that would affect live critters.  My guess being you want Free Chlorine testing for anything living. So, it's probably more about if topping out at 0.5PPM is high enough. 

[anewbie]

On 5/19/2023 at 5:29 PM, dasaltemelosguy said:

OK. Then I guess it's all about the upper range and if that's good enough for your purposes. Maybe so as you won't want 0.5PPM around anyway. 

But Free is more important to know than Total. Total chlorine is similar to the ammonia tests that include ammonium.

A Total Chlorine test combines the free chlorine and any chlorine compounds it created while disinfecting or reacting with the water. These compounds may not be harmful, or they may be. It's just like the ammonia tests when you could read a high value but it's not ammonia but rather, ammonium. It reads high but you can't tell which form of ammonia you've tested. So, Total doesn't tell you much about chlorine as a dangerous compound. Total tends to be more about swimming pools. 

Free chlorine is the active disinfectant that is not 'used up' yet. So Total is considered less useful and may be inaccurate insofar as testing chlorine levels that would affect live critters.  My guess being you want Free Chlorine testing for anything living. So, it's probably more about if topping out at 0.5PPM is high enough. 

Interesting; your answer is opposite of their fish representative. Now i'm not sure who is correct 😉

When i suggested 762 - they said:

"The 762 only measures free chlorine, which is the most dangerous form, but glosses over other molecular forms that could have an affect So I would suggest the 761" but you are sort of saying the exact opposite - only the free chlorine is harmful and these other molecules are providing a false reading. Of course the converse is the "all chlorine" test would provide an upper bound so you know it is no worse than the value and if these other molecules can become problematic later (can they become 'free' later on from a chemical perspective) are they an issue? Looking at 701 it does say 'free'; but they also suggest pool and spas as the application (using their website); for 761 they toss in education, industrial and again pool and spa which they also repeat for 762 - not very useful. In fact the entire fact that I'm unsure if they know what they are talking about i posted this note on the forum here. You have three models 701,761, and 762 and it is not clear which one is most suitable. My concern with the 701 when i first saw it is that at 1ppm (the lowest resolution of this model) the chlorine might still be harmful and you really want ppb but now this issue of free chlorine and bonded chlorine is making my head spin because I don't know if it matters that much at the end of the day. When my water pass through a bed of charcole will it fail to absorb bonded chlorine and will that mean the 761 reading will be off the wall and does it matter if the chlorine is bonded in some fashion or is it still dangerous as their representative claim. Perhaps worse but maybe not - if i wanted to measure the effect of something like prime i suspect from what has been said 761 would measure near tap water level of chlorine while the 762 would measure near 0 ?

Edited May 19, 2023 by anewbie

[dasaltemelosguy]

They would probably know if the types of chlorine included in Total affect aquatic life more than I would to be honest. Generally, those are considered inert but I'm not really sure. The 701 does read as low as 0.01PPM so that seems plenty low but again, I'm no expert on if the chlorine compounds affect fish. For example, the chlorine in salt may even affect the reading in a Total read. Or other chlorides that may or may not be harmful.

Free most certainly is the toxic one but the others may be important too. This is from the 701 resolution specs:

Range 0.00 to 2.50 ppm (as Cl2)

Resolution 0.01 ppm

Accuracy ±0.03 ppm ±3% of reading @ 25 °C (77 °F)

Then again, I suppose if you get a good Total reading, then you're safe no matter what so perhaps they're correct.