Measuring Cyanuric Acid - can this help?

[smallpooldad]

When measuring a low level (35) of cyanuric acid it is often hard to know if there is any level at all as the test can wash out with FC of 5 or above. Would adding 5 drops of thiosulfate from the alkalinity test help?

[waterbear]

Where do you get that the CYA test will wash out when the FC is 5 or above? Not true!

[smallpooldad]

Ok lets split the difference - hard to differentiate. You are right about washed out, it maybe a poor choice of words. But as of yet the chemical question is not answered. Oh and I got it from doing repeated tests with a new Taylor kit eg. below 30, about 32, possibly 35, etc. It could be, as you stated, that it is not the FC, it might be something else but I believe I read somewhere in the forum higher FC makes it more difficult to get a true reading this is certainly true when doing a hardness test.

[waterbear]

Chloirne levels will have no effect on the CYA test. it does not use an indicator that can bleach out. High chlorine levels can and will affect both the TA and pH tests but does not have any effect on the CH test if it is an EDTA ttitration. It can affect colormetric CH tests such as used in the LaMotte colorQ.

[smallpooldad]

WaterBear,

Thank you for the clear explanation. But any ideas as to why the readings are so inconsistent within minutes of each other?

Aloha

[waterbear]

has to be testing error or the vial is not clean and dry after the first test. How inconsistant are we talking, anyway?

[CarlD]

I agree with Evan. Something is wrong.
Do you always rinse your test vial, squeeze bottle and squeeze bottle top both before and after you run the test--every time?
Do you shake the pool water/reagent mix for at least 30 seconds before running the test?
Do you keep your reagent in a cool, non-sunny place?

Correct CYA technique involves holding the test vial at waist level, facing the sun, and you do the test in direct sunlight, if you can.

Fill the vial slowly WHILE HOLDING IT AT YOUR WAIST. I like to move the bottom back and forth to see the dot better--movement is easier to see through the cloudy water than non-movement. When I cannot make out the dot I'm done.

I repeat the test by pouring the fluid from the vial back into the squeeze bottle and repeating.

I always do it this way. Therefore my measurements vary from the amount of CYA, rather than my technique.

So even if my technique isn't perfect, the continuity of HOW I do it reveals changes in CYA fairly consistently.

[smallpooldad]

Thank you both and a happy 4th.

Well the mystery continues. Did two test as you perscribed, dry, very clean, and in the sunlight.

The first with a Taylor kit R-0013 the result was 30 ppm. Then with my neighbours Pentair Water kit the result 25 ppm.

Which should I believe.

[waterbear]

Pay very close attention. THE TEST IS NOT THAT ACCURATE. You have essentially the same results. Call it 30 ppm and call it a day! A differenece of 5 or even 10 ppm on a CYA turbidity test is nothing to lose sleep over. I would not even worry too much about a 15 ppm difference. A $1000 LaMotte Waterlink Express (as used in many stores) has an accuracy of +10/-25 ppm for this particular test!

[smallpooldad]

Thank you.

This makes it very clear I will split the difference and call it 27.5. Now I can finally get a good nights sleep.

Aloha.