Yet another chlorine post.........................

[sktn77a]

OK, so I'm going cross-eyed reading all the chlorine posts on here! I have a question that I haven't found covered yet.

First of all, I just had my pool renovated. Fiberglass walls were removed and replaced with shotcrete and the whole pool was plastered. Pool was filled with city water (pretty good) last week. PB added some CYA and level just now is on the low side of normal. Chlorine was added and that's where the confusion starts. I hava an OTO test which shows chlorine to be 3-5 (a little higher than I would like at the moment). When I use the HTH test strips, it shows combined chlorine to be VV low and free chlorine to be low (about 0.5-1 as best as I can tell). PH is 7.6. Which shoulde I believe? I'm inclined to believe the OTO test.

Also, the OTO test kit says read the color after 5 seconds and this is free chlorine; Wait 5 minutes and read again and this is total chlorine. I take it that this is..... shall we say....... errrr....... optimistic?

 

[domct203]

OK, so I'm going cross-eyed reading all the chlorine posts on here! I have a question that I haven't found covered yet.

First of all, I just had my pool renovated. Fiberglass walls were removed and replaced with shotcrete and the whole pool was plastered. Pool was filled with city water (pretty good) last week. PB added some CYA and level just now is on the low side of normal. Chlorine was added and that's where the confusion starts. I hava an OTO test which shows chlorine to be 3-5 (a little higher than I would like at the moment). When I use the HTH test strips, it shows combined chlorine to be VV low and free chlorine to be low (about 0.5-1 as best as I can tell). PH is 7.6. Which shoulde I believe? I'm inclined to believe the OTO test.

Also, the OTO test kit says read the color after 5 seconds and this is free chlorine; Wait 5 minutes and read again and this is total chlorine. I take it that this is..... shall we say....... errrr....... optimistic?

Your FC target should be based on your CYA level. What is your CYA level? There really is no 'normal' CYA level, CYA is dependent on location & sun exposure. If you have the minimum recommended CYA level of 30ppm, you should be maintaining a FC target of 4-6ppm every day.

[FC/CYA][/FC/CYA]

The OTO test is not a very accurate test for chlorine, and the test strips are even worse. As you mentioned, it is very hard to tell the difference between FC & TC on the OTO test.

Use your FAS/DPD test and post a complete set of test results.

 

[Jimrahbe]

Keith,

So, you have been a member since 2010 and you don't have a good test kit???

In all your cross-eyed reading, did it not become clear that an accurate test kit is what makes or breaks the TFP pool care process?

The OTO test is just to give you a basic reading that shows 'about' what your FC reads. You must have a FAS/DPD test if you want an accurate reading.

Thanks,

Jim R.

 

[sktn77a]

Yes, I signed up in 2010 to ask one question but haven't been back on the forum until a couple of weeks ago. So not an informed expert on pool chemistry by any means.

Honestly, even on this forum, I've read caveats and limitations of the FAS-DPD test so I'm confused. I've looked at the Taylor kits and may get one but am hoping for some insights on my present numbers in the meanwhile.

 

[duraleigh]

There are no caveats or limitations on the FAS/DPD test. It is the most accurate test you can purchase (for our purposes) and will precisely nail down any confusion you may have.

Don't get "one of the Taylor kits". Get the TF-100 from TFTestkits or the K-2006 from Taylor.......those are just about your only choice to learn to manage your pool with our TFP methods.

 

[AftonJeeper]

I trust the OTO more than any guess strip. But most only use it to see if they have chlorine in the water, not how much.

For reference I try to keep my FC around 5 during the swim season, so 3-5 would be on the low side for me.

Head over to tftestkits.net and get your self a TF-100 with speedstir. There will be no more guess work. The Taylor K2006c is a good test kit too, just make sure you get the speed stir. It makes testing much easier.

Do some more reading in pool school, best place to start is ABCs of Pool Water Chemistry.

 

[domct203]

........Honestly, even on this forum, I've read caveats and limitations of the FAS-DPD test so I'm confused.

Please elaborate & share links to topics on this.

The FAS/DPD chlorine test is the test all others are compared to. It uses industry standard Taylor reagents, and will accurately measure FC up to 50.0ppm in 0.2ppm increments.


The test strips are terrible with FC, and lack the resolution needed to reliably manage your pool. The only satisfying result I have ever seemed to get out of them is by viewing them in the trash bin.

The OTO test is really not much better, and is primarily used as a Yes/No test. If it turns yellow, yes there is chlorine. It is not however very accurate to tell 'how much'. I use it during the week to make sure my SWG is running properly, then run the FAS/DPD 2-3 times over the week to get accurate FC & CC measurements.

During peak season I use the FAS/DPD test just about daily, always staying on top of the FC generated. When I was manually dosing the pool, I used the FAS/DPD every day for the entire season.

 

[Donldson]

OK, so I'm going cross-eyed reading all the chlorine posts on here! I have a question that I haven't found covered yet.

This question gets covered several times a week.

Test strips: inaccurate, imprecise, unreliable junk.

OTO: Accurate but imprecise. It will reliably tell you there is chlorine and give you a pretty ballpark idea of how much is in it, but it is not precise and prone to misreading.

FAS-DPD: Accurate and precise. It will tell you your FC level to within 0.2 ppm (when using a 25 ml sample) and your CC level to the same precision. There is no guessing colors or waiting 5 minutes to see if you can find the CC level. It is the golden standard of TFP testing, the most accurate and precise test of the bunch.

 

[sktn77a]

OK, I'm ordering the T-100 kit! Will report back when I get more detailed results.

 

[domct203]

OK, I'm ordering the T-100 kit! Will report back when I get more detailed results.

Awesome!

The CYA test is the trickiest. Make sure you are testing it outdoors on a bright sunny day, back to the sun, viewing the vial at about waist height in your shadow. I fill the vial to 100, then glance for the dot. If I see it, I fill to the next line (90) and glance for the dot. If I see it, I repeat with each level until I no longer see the dot when glancing for it. If you stare for the dot your eyes will play tricks on you.

Let us know if you have any testing questions.