I tested for CYA using the CYA reagent and vial with the black dot on the bottom. I transfered the liquid to the vial and noticed the water was so clear I could see the black dot even if i filled it beyond the graduation level on the vial (30). So this indicates I have at least <30 ppm of CYA. The water wasen't even the slightest cloudy beyond 30. So I can only asume that it could be 20, or 10 or 0. Based on the pool calculator on a 13,500 gallon pool to raise by CYA by 10ppm It indicates I need to add 18 oz by weight of CYA or 19 oz by volume. I'm thinking (just to be safe). I should add cya in increments of 10ppm until it registers on the test (is supposed to take a week). Then I can go from there.

I'm also curious on the values the pool calculator is giving me. OZ is a measurement of mass. So I add 18 oz? how do I add 19oz by volume? What does that mean????

by volume means you use a normal measuring cup. 8 oz by volume = 1 cup.

Originally Posted by Melt In The Sun
by volume means you use a normal measuring cup. 8 oz by volume = 1 cup.
So pretty much If I'm using this stuff HTH Pool Stabilizer and Conditioner (http://tinyurl.com/86mdvv3). I need to use 2.37500 cups of the stuff to bring a 13500 pool to 10 cya?

Yes, 2 3/8th cups of that will be right around 10 ppm of CYA.

Keep in mind that granular CYA can take up to a week to fully dissolve and show up on the test. Generally what you want to do is add about 2/3rds of the total amount you think you need, wait a week, test to see where you ended up, and then make a second adjustment from there.

Originally Posted by JasonLion
Yes, 2 3/8th cups of that will be right around 10 ppm of CYA.

Keep in mind that granular CYA can take up to a week to fully dissolve and show up on the test. Generally what you want to do is add about 2/3rds of the total amount you think you need, wait a week, test to see where you ended up, and then make a second adjustment from there.
Thanks,

Originally Posted by JasonLion
Yes, 2 3/8th cups of that will be right around 10 ppm of CYA.

Keep in mind that granular CYA can take up to a week to fully dissolve and show up on the test. Generally what you want to do is add about 2/3rds of the total amount you think you need, wait a week, test to see where you ended up, and then make a second adjustment from there.
OK, I'm getting different readings. I just spoke with HTH over the phone. They indicated to increase the cya to 30 ppm on a 13500 pool I need to add 62 oz of hth stabilizer. But the pool calculator is showing me 56oz by volume?

They indicated to increase the cya to 30 ppm on a 13500 pool I need to add 62 oz of hth stabilizer. But the pool calculator is showing me 56oz by volume?
It doesn't matter. The accuracy of the test is plus or minus 10ppm at best so you waon't be able to detect the difference.

YOur CYA measurements do not have to be precise. If you shot for 20ppm and get 25ppm, that's fine.....30 is not a deal breaker, either. If you shoot for 20 and get 40, well.....really?

Once you begin your shock process, your FC dosages can be a little more accurate but, again, they do not have to be of the precision you are targeting.

I have forgotten, have you done a recent pH test?

Originally Posted by duraleigh
They indicated to increase the cya to 30 ppm on a 13500 pool I need to add 62 oz of hth stabilizer. But the pool calculator is showing me 56oz by volume?
It doesn't matter. The accuracy of the test is plus or minus 10ppm at best so you waon't be able to detect the difference.

YOur CYA measurements do not have to be precise. If you shot for 20ppm and get 25ppm, that's fine.....30 is not a deal breaker, either. If you shoot for 20 and get 40, well.....really?

Once you begin your shock process, your FC dosages can be a little more accurate but, again, they do not have to be of the precision you are targeting.

I have forgotten, have you done a recent pH test?
Yep, Yesturday it was 7.2.

The difference is probably that the Pool Calc uses 100% cyanuric acid in its calc and HTH probably used the actual percentage in theirs.

But as Dave said, a difference that small really doesn't matter.

Originally Posted by Bama Rambler
The difference is probably that the Pool Calc uses 100% cyanuric acid in its calc and HTH probably used the actual percentage in theirs.

But as Dave said, a difference that small really doesn't matter.
It kind of makes me wonder if we need to find a chemist to do some complex mathematical calculations to determine how much CYA do you actually need? Maybe there's a sweet spot that is perfect and will cause maximum TC benefit and minimize TC dosages?

Originally Posted by steppinthrax
Originally Posted by Bama Rambler
The difference is probably that the Pool Calc uses 100% cyanuric acid in its calc and HTH probably used the actual percentage in theirs.

But as Dave said, a difference that small really doesn't matter.
It kind of makes me wonder if we need to find a chemist to do some complex mathematical calculations to determine how much CYA do you actually need? Maybe there's a sweet spot that is perfect and will cause maximum TC benefit and minimize TC dosages?
No two pools have the same climate, bather load or fill-water chemistry. All you can do is take the vales in the chart and see what works best in your pool.

In our efforts to be as precise as possible, we tend to overlook that we can only crudely calculate the amount of water involved. A water level difference of 1 inch for a 15' x 30' pool is more than 250 gallons. The precision of trying to dose to the ounce or CC or drop, or, whatever, is still limited by how closely we know the amount of water to which we are applying it.

Originally Posted by Ohm_Boy
In our efforts to be as precise as possible, we tend to overlook that we can only crudely calculate the amount of water involved. A water level difference of 1 inch for a 15' x 30' pool is more than 250 gallons. The precision of trying to dose to the ounce or CC or drop, or, whatever, is still limited by how closely we know the amount of water to which we are applying it.
Excellent point ... I would be amazed if I was within 1000 gallons. With the freeform and variable depth in ground pools, this certainly can be a challenge.

You can almost get a better idea of the volume by dosing certain chemicals, measuring the results before and after, and playing with the pool calculator pool size to get the numbers close.

You are absolutely correct; it's a big reason for doing one's own testing and pool maintenance. You get to know your pool, and develop a feel for how it behaves and what it needs.

OK, I got the HTH stabilizer. It's 96% Cyanuric Acid, I guess that's why their dosage is higher. Anyway I put two cups in a sock and hung it over my return. In roughly 2 hours it's mostly all out from the sock. So I need to wait a week before I test?

So I need to wait a week before I test?
Well, no. You can test anytime you want to check yourself. Experience on the forum seems to be that the CYA test isn't valid for anywhere from 2-7 days.