CYA level - which result to use

[Luric]

I received my TF-100 a few weeks ago, excitedly did all my test and posted my levels for advice (thanks for everyone's help!). Before posting my CYA results, I did the 7065 control test to be more confident in my own CYA reading. I felt confident in my almost non-existent CYA result (tube filled entirely, could still slearly see black dot, but the water was a little cloudy). Per some suggestions to take it slow in raising my level, I added 4 lbs and tested again. I've gotten readings ranging from 20-30, however my readings with the 7065 test using replacement CYA reagent have been 35-45, so I've been a little skeptical of either my replacement r-0013 or my own ability to read the test since we're new at this. My 1st round of testing where the 7065 test was accurate and my pool water filled the tube are the only 2 times I used the included r-0013. My husband accidently dumped it a few days later, so we tested everything again once the replacement from Amazon came.

Since I want to get my CYA to a good level, and I'm lacking confidence in my own readings, I took samples to 2 different pool stores yesterday. Both places gave me readings in the 40s (42 & 44). If that's the case, then I don't want to do anything further and risk overshooting my CYA. But if my own novice reading is more accurate at 20-30 then I really do need to add some stabilizer.

I know pool store testing is frowned upon here, but in this case, with a subjective test that I've already had issues reading the control test accurately, should I go with the 2 similar pool store levels? Other suggestions? Anybody in central NJ wanna come out and do the test again for me?

 

[Mr Bruce]

.. my readings ... have been 35-45..

Then that's the end of it. Call it 40 and stay out of the pool store

 

[Luric]

The 35-45 readings I was getting was for the 7065 test that should be 50. The stores got in the 40s with my pool water which I was getting between 20-30. I'm going to test my pool's CYA again once shortly to see what it looks like once it hits 40. Maybe I just have xray vision!

 

[Mr Bruce]

I understand, you were getting 40 with the control, 20-30 with your pool water. In that case I would call it 30 and not worry too much about it.

FYI, the CYA test is the one the pool store seems worst at. I would not use them as a data point.

 

[cj3737]

When you do cya, make sure you stand in bright sunlight (if available) with your back to the sun, shading the test tube. Start slowly and only do a few drops at a time until the dot starts to disappear then do one at a time... the moment the shadow of the dot disappears, stop and read it... If the level is between lines, use the next highest level... IF its between 30 and 40 , use 40 as your CYA level... the kits aren't designed to read "35". Don't trust pool stores unless you want to spend money... they don't care what your pool looks like.. They just want to sell product..

When adding CYA, shoot lower than your target and work your way up... CYA doesn't just disappear unless you change water so if you over shoot, you will have to use more chlorine to maintain

 

[Griswald]

The biggest issue that is seen is using the scale on the CYA tube as a ruler.

It is NOT!!!

It is a multiple of 10, anything over the line is assumed to be the next highest 10. If you get a "42" on your test, that is really a 50.