Help reading FC/Ph colors

[AlbertSteg]

I find myself second-guessing a lot about what shade the solution in my test block matches up to. My general impression here is that my chlorine is ok but I need to adfd some acid.

Cl: 2.5? Or more like 4?
Ph: 8.0? Or is the Ph way off the charts at 9+?

 

[PoolStored]

pH is 7.9 to 8.

Ignore the yellow OTO FC test. Use the FAS-DPD 870/871 powder and reagent for FC. 10mL sample, each drop is .5 FC. Use your speedstir.

 

[ajw22]

Use the FAS/DPD drop test for all chlorine values. All the OTO color test tells you is the you have chlorine in the after.

I say your pH is 7.8. It does not have the purple hue of 8+.

You need to put a white background behind it for better color matching and not the blue sky.

 

[Newdude]

Use a thumb from each hand to block off above and below the one you want to compare. I find yes/no way easier than best of 3. For example :

More pink than 7.8



Less purple than 8.2



So you're between the 2 and on the fence for dose time. If you dose a couple days early, your penance is next time comes sooner too. If you dose a couple days late, Ph is a long term concern and I assure you the price of beer will remain unchanged either way.

 

[pjt]

A consistent background is key. To get good backlighting, hold the block in front of your computer monitor/tablet/phone with a blank white screen displayed. Also, try holding the block sideways or upside down. Sometimes that helps distinguish colors better. I also use two old hotel keycards to mask off areas and narrow down my decision.