FC Testing Q

[Tom Tank]

New pool owner and recent convert to the TFP method. Using the TF100 test, my CYA=100, so I know I need to drain water, but really don't want to do that until the season is over. So I am left with maintaining a pretty high FC between 7-12. My questions are: Because my FC level needs to be higher than 5, do I have to use the FAS/DPD daily? Is there a way to dilute the water and use less of the drops or use the OTO test for chlorine that is higher than 5. Thanks.

 

[Smykowski]

Just use the FAS-DPD. I've been on TFPC for 3 years and I've never done an OTO test. When you're wrestling with a CYA that high, you really need accuracy and precision in that upper range.

 

[Tom Tank]

Is there a way to dilute the water for testing for FC? I am in the middle of a SLAM and have to maintain a FC=39.

 

[RobbieH]

You'd have to use distilled water, tap water will have FC in it.

Are you sure you are at 100? Have you tested CYA with a 50/50 tap/pool water mix?

 

[Tom Tank]

I have tested CYA with the 50/50 mix and it was a little under 100. For FC testing, what would the calculation be if I used 50/50 mix in the 10ml tube? Is it 1:1?

 

[jblizzle]

Until you need the accuracy to know you are done (for the CC test and OCLT), you can just use 5ml of water where each drop is 1ppm.

 

[Abigail K]

I have tested CYA with the 50/50 mix and it was a little under 100.

If I understood that correctly, your CYA reads slightly under "100" with a 50% dilution, it means your CYA is actually ~200ppm (or more).

 

[Tom Tank]

Sorry if I wasn't clear enough, CYA was slightly under 50 so I doubled it to 100 since I was using a 50/50 mix. Is that the correct?

 

[Abigail K]

Yes, that is correct.

 

[pepsiholic]

Sorry... deleted post