Oto test

[qwertyjjj]

If OTO only tests total chlorine, is it possible that it could tell me that my chlorine is at 5ppm whereas actually I have no free chlorine in the pool at all thereby giving me a false indicator?

Also, when chlorine evaporates, is it all chlorine or just the free chlorine? I'm assuming evaporation would reduce total chlorine?

 

[jblizzle]

You are correct that the OTO can not really differentiate between FC and CC ... although CC is almost always near 0 unless something has gone VERY wrong.

Chlorine does not evaporate ... so I am not sure what you are really asking in your second line.

 

[Donldson]

Trying to get specific numbers with the OTO test is a recipe for a bad time. Many have banged their heads against the wall because they felt the shade of yellow they saw did not match what their FAS-DPD test showed, despite us telling them the OTO test is not really meant to give an accurate measurement. However yes, the answer to the first question is that it is TC can be any combination of FC and CC and that's why occasional FAS-DPD testing is important to confirm everything is where it should be.

If your second question is regarding UV burnoff, then the FC is partially protected by the CYA while the CC is less protected so burns off faster. That's why CC is rarely a problem in properly managed outdoor pools but can be a problem in indoor pools regardless of their management. Any reduction of FC or CC necessarily results in a reduction of TC.

 

[qwertyjjj]

I'm basically worried that I could get a reading saying I have good chlorine levels when in fact I have zero FC and it's all CC.
Why is CC near zero in an outdoor pool?

 

[Donldson]

You are testing occasionally with your FAS-DPD test, right? If so then that is not going to happen. However if that is a concern then you can test daily with the FAS-DPD test.

 

[ashtonfitzgerald]

Understanding the limitations of the oto test allows you to better manage your pool. Checking the FC level after a heavy swimmer load will give you a false reading. FC could be 2, CC could be as high as 2 depending on how dirty the swimmers were and the size of your pool.

My small pool is a good example of that--a few bodies with sunscreen can create a lot of CC due to the dilution being so low. I rely on the FAS-DPD to help me gauge the required CL additions. Oto will tell me I have 6ppm CL when in reality I'm close to the low end of my target. I've seen it happen.

 

[DeanP66]

IMO, the OTO test is a total waste of time. You can run the extremely accurate FAS-DPD test just as quickly and actually get a good read on the results.

 

[jblizzle]

What is your pool size and details?
What test kit are you using?
Your signature is empty

 

[YippeeSkippy]

The OTO test is handy when you just want to see "pink! yup, something chlorine-like is in there!" BUT you don't necessarily need to know how much FC or CC specifically.

....Example would be after soaking in the hot tub.

Capisce?

Maddie

 

[DeanP66]

Why not just do it right the first time and know exactly if you have 1 PPM of FC and possible algae starting, or 4 or 5 PPM FC with no worries. Why take the extra step? It might take ten extra seconds to know for sure without just wondering.