cyanuric acid test

[David Hughes]

So as a guest, I took advice given here and went to Walmart and purchased a HTH-6 titration kit and dumped my strips. I am having recurrent issues with Algae, no big surprise given the chemistry, and my first use of the HTH kit told me pretty much what I thought about my pool water at the moment. Very low (7.0) PH, low to no chlorine levels, (although I distrust the reading due to PH being off). TA is 60. Total Hardness around 240. So here is the one that gets me, and I thought I'd ask before I just started massive dosing with stabilizer. Tested twice, I just can't get ANY reading of CA with this kit. I tested my water supply as well as a check, got nothing. I wouldn't think any of this is odd. We have never used stabilizer, get a ton of rainwater which causes dilution when the pool overflows, and since my water supply is cistern-collected rainwater typically full of sahara dust and monserrat volcanic ash (alkaline), we are forever adding acid to correct PH. EXCEPT that all summer we have been using chlorine pucks to boost chlorine levels as a supplement to my SWG, and I thought this was supposed to have a CA component, which is not showing up....

Should I believe the test and start adding CA?

Thanks, David.

[Watermom]

No need to test fill water as there will definitely be no CYA in it. Just to make sure you are doing the CYA test correctly, can you explain your testing steps? Also, what is the volume of your pool and how many pucks do you think you have used?

[David Hughes]

Pool is 28k gal cement in ground. Tested per the instruction. Filled test bottle to 7 mil mark, added reagent to 14 mil, shook for 30 seconds and added to turbidity tube to make black dot disappear. I have zero cloudiness in the reacted sample, so the dot is visible even though the tube is full.

[Watermom]

For now, I'd say deal with the algae and then worry about adding more CYA after that. You need to shock your pool. Any reading below 30ppm will not be detected on the CYA test so you can't assume that you have 0 but rather have to assume for now that you may have almost 30ppm. Go ahead and shock the pool up to around 15ppm. You can't shock a pool with trichlor tabs. Might want to use bleach as your source of chlorine to shock with. Do you have Walmarts in your area? Each of the 121-oz jugs of their generic 8.25% bleach will add about 2.8ppm of chlorine. You can use that as a reference to help you figure out doses of bleach to add whenever you test.

A couple of links that will help:>
http://pool9.net/cl-cya/
http://pool9.net/tk/ (Not sure if you can ship this kit to the Virgin Islands or not?)
http://pool9.net/oto-chart/

(Until your registration is completed, you won't be able to see the rest of the forum or follow links while you are logged in. So, copy the links and paste them into a browser window after you first log out.)

[PoolDoc]

Registration updated . . .

A couple of further notes:

1. We've long recommended store brand bleach, to avoid the confusion of all the Clorox brand 'flavored' bleach. But Walmart has begun selling some non-bleach bleach. SO . . . be SURE to check for the chlorine % -- on almost all current household bleach products, you should see "8.25%" if you are buying the correct item.

2. You need to check your chlorine puck container, and tell us EXACTLY what the listed chemicals and %'s are. Pool chem makers constantly play ingredient games with their product, so with out that exact list, we don't know what you've been using. This is especially true since you are outside the continental US.

[David Hughes]

I'm not much concerned with the pucks. I don't use them when I am around, and pretty much provided them as a way for my caretaker to boost chlorine in the event my swg was behaving inconsistently due to the need for filter cleaning, since my guy doesn't know how to do that.

So we dosed the pool with Borax and cya and liquid chlorine bleach. The chemistry all settled perfectly in recommended ranges for mild shock, and the algae is quickly clearing up. And now I am starting to understand the value of stabilizer, which means I will be able to run the pump and swg much less and maintain chlorine levels. Pretty important at $. 54/kwh!

I really appreciate how you guys take an arguably very complex situation and drill it down to its most simple components! Thanks so much!