Confused about target FC

[AlbertSteg]

Okay, I've been told to ignore the Comparator Block and use the "Chlorine Drop Test" to measure chlorine instead, but still I'd like to understand a little better what it is I'm aiming for. The comparator sample in the picture looks like around a 4 while the Drop test yielded a 6.5. Okay, that seems like a big difference and I should trust the drop test....

But the Comparator block indicates a range of 1 'Min' and 3-4(?) 'max' while the Chlorine/CYA calculator in this site recommends a range of 3-7 for my level of CYA . . . which it suggests is too low for an SWG pool like mine. Okay. . . . but when I check the recommended levels for CYA 60+ and the figure goes up to the 4-12 range. It seems the recommended levels for liquid chlorine pools also have 4 as a minimum.

So, why is the Comparator block scale pitched so low? is it based on outdated views about the ideal levels? Given that it appears so inaccurate I'm guessing I'm better of using the test strips for a quick daily check (I'm not going to do a drop test every day) -- it suggested 5+ today, which is better than the comparator. It's confusing to buy this highly respected kit and then hear that part of it is so useless.

 

[Texas Splash]

It's confusing to buy this highly respected kit and then hear that part of it is so useless.

The comparator block isn't useless. Three are some key points about it that many (new) pool owners don't understand:
1 - It has a limited FC reading. The viewing block areas are industry standard levels and that's all you get.
2 - It only shows total chlorine, therefore a person could assume their FC is high when it's not. The CC might be what's throwing the level off.

We encourage owners to first become familiar with the FAS-DPD because we know it is accurate. Then as an example, say your daily FC range should be between 6-8. If you do the comparator test at the same time, you can visually gauge the shade of yellow. With enough practice, you can feel somewhat confident of the yellow shade and perhaps use the FAS-DPD every 2-3 days as opposed to every day to help save reagents.

Some owners just use the FAS-DPD everyday, but it's an option.

 

[Donldson]

The OTO chlorine test is not very precise, though it is accurate in so far as it will indicate the presence of chlorine and a very broad indication of how much. As you saw though, it's got a large margin of error. Taylor is also beholden to the industry boilerplate numbers on their products. It's the proper range in water with zero CYA, but even a small amount of CYA can make that range unacceptable for maintaining sanitary and clear water. Follow the recommended FC levels based upon your CYA level.

Given that it appears so inaccurate I'm guessing I'm better of using the test strips for a quick daily check

Absolutely not. Test strips aren't good for anything, throw them away.

The OTO test is NOT useless. Once you get to understand your water you'll fall in to a bit of a pattern where you typically need to add roughly the same amount of chlorine each time. Then you can use the OTO test to see if it is roughly the same color every day. Don't use it to try measuring the chlorine, just use it to make sure there's no big changes one way or another and confirm the actual level once or twice a week with the FAS-DPD test.

 

[Jquinby]

Some owners just use the FAS-DPD everyday, but it's an option.

We went this way. Once my wife learned about the FAS-DPD test, it's all she uses now. We also tend to keep the chlorine a bit higher than the comparator comfortably shows because of the amount of kid/grandkid traffic in the pool.

 

[Newdude]

But the Comparator block indicates a range of 1 'Min' and 3-4(?) 'max

It's Taylor's block using standard issue industry recs.

We set a min FC per your CYA. You need to dose over that, to remain free and clear of it after your daily UV loss.

3 ppm may last a week in April
3 ppm may last 3 hours mid day in August

You adjust the target accordingly. Leave some wiggle room. Poolmath suggests a wide range because it doesn't know the time of season or your yard conditions (shade?).