CYA Mixture Accuracy?

[DonW]

I'm trying to get an accurate reading on my CYA level, and want to do the test the same way with the same lighting source and the same amount of pool water & R-0013 for the sake of consistency. Evidently I stink at consistency and reading tests because I get wild swings in readings. Doing a quick search I found Jason's prescribed CYA test: extended-test-kit-directions-t25081.html
In it he describes a 15 ml pool water and 15 ml R-0013 ratio. Cool. So I go to measure my CYA test bottle and the instructions say fill to the bottom label with pool water and to the top of the label with R-0013. So now I measure those amounts and the ratio comes up to be 15 ml pool water and 18 ml R-0013. My ratio is and has been off. What's my CYA level? I don't know!
Could someone please clarify for me what level of water sample and reagent is accurate? I'm not doubting Jason, but from 2 sources of TFP I'm getting a confliction. For some reason I had written on my CYA test instructions, 14.6 ml pool water and 14.6 ml R-0013. I haven't a clue where that came from.

 

[linen]

Also from the extended test kit directions:

The precision of the test, when done correctly, is around plus or minus 15 for levels up to 90 and plus or minus 30 for levels between 100 and 200. Novices often have problems reading the test correctly, and tend to get higher than actual readings.

So don't get to hung up on this, but the ratio should be 1:1. Could be exact placement of label (if it is the tl-100 kit), etc., but probably not a big deal. As long as you mix 1:1 and get enough total fluid to get the water column above your end level (which goes down as water level goes up) you should be fine. However, using smaller total amounts will add to inaccuracy, since ratio errors would be magnified.

 

[DonW]

Thanks for the reply. Normally I wouldn't be such a spaz with this, but I just finished a bout with mustard algae, (my 2nd in 3 years) and felt I need to get a better grip on my CYA level. I thought about retracting the question and then you replied. I have since marked my CYA testing bottle with a sharpie to indicate a 15 ml mark and another 15 ml mark above that, regardless of where the label is. 1:1 ratio

 

[linen]

Normally I wouldn't be such a spaz with this, but I just finished a bout with mustard algae, (my 2nd in 3 years)

That doesn't sound fun. Any idea of why this is a reoccurring problem?

I thought about retracting the question and then you replied.

I am glad you did not, probably a good one for others to see...

I have since marked my CYA testing bottle with a sharpie to indicate a 15 ml mark and another 15 ml mark above that, regardless of where the label is. 1:1 ratio

Great idea! I am going to check mine too!

 

[Puffin]

If you're worried, pre-measure the sample. I take the test vials that came with the TF-100, fill it with 20ml of pool water. Then add the CYA reagent to take it to 40ml. I mix in the vial (Using the speedstir) then it pour into the mixing bottle. After adding the mix to the bottle, proceed normally.

I use a speedstir for pretty much all of my tests. I was asking if I could use it to do the CYA test and this is the suggestion I got. The key to this one is that the ratio is 1:1 pool water to CYA reagent. With this knowledge, you can to any sample size you want. If you know your CYA is high, you can use much less water/CYA reagent. Since I use the speedstir, it is mixed before I add it to the bottle, if you're not using the speedstir, you might want to try 15ml water and fill to 30 with the CYA reagent to make the bottle will hold the entire sample. 40ml of mix, always leaves a little in the test vial.

 

[DonW]

Puffin, great idea! Now I have to get a speedstir. Wait, I'm broke from buying 112 gallons of 6% bleach to deal with my last round of MA. Maybe Santa will be kind to me this year.
Linen, my FC level fell to its lowest point of 3, which I'm guessing was below the FC cut-off. Kinda why I was looking for a specific ratio. Thanks to all for craifying the 1:1 ratio

 

[linen]

Puffin, great idea! Now I have to get a speedstir. Wait, I'm broke from buying 112 gallons of 6% bleach to deal with my last round of MA. Maybe Santa will be kind to me this year.

Maybe santa can throw in a intex swg as well Mine has been great for me.

Linen, my FC level fell to its lowest point of 3, which I'm guessing was below the FC cut-off. Kinda why I was looking for a specific ratio. Thanks to all for craifying the 1:1 ratio

Sounds like you might be already thinking this way, but I would try and get that CYA level down a little by next season.