CYA test is pretty subjective, isn't it?

[Lenny]

As the title of Ben's "best guess" chart implies, this isn't an exact science so there wouldn't be much point in worrying about perfection with this test.

So far, I've been able to get consistent readings as long as I test in similar light conditions. If I run into algae problems, I'll run the chloring levels a bit higher. No biggie.

[geoeremite]

What do you considered "disappeared"?

This is the question I still wonder about. Which of the following have "just disappeared"? (Click on the photo to get a larger copy.}


Empty, 50, 40, 30, 20

What do you think?

cheers,
Scott

(I'll leave the picture up as reference if we come to consensus.}

[CAL7]

My $.02 is that it doesn't disappear until the last (20ppm) shot.

[cwstnsko]

Probably somewhere between 20 and 25, and that's probably as accurate as you need to be to know where you stand

[mrmrk49]

I would have said "keep going, I can still see outline of the dot"

Excellent pictures by the way!

MikeK

[cygnusecks]

Cool pictures.. I thnk I'll post them next time I have to "make the call".

Someone said I can dump my test water back into the squeeze bottle and re-use it???? So I *never ever* have to buy reagent ever again?

[edarling]

cygnusecks - I believe they meant that they can use the same sample to take another look at the results in case of doubt. You have to do it all over again for the other tests, but this test you can just add the same sample back into the tube to see if your eyes see the same thing.

My question always has been - how high is waist high? I'd rather Ben put a number like 2 feet, 18 inches, etc. on the instructions. I'm over 6', but someone else may be 4'6" and have shorter to their waist.

Glad to read that it is as subjective as I thought.

[waterbear]

Regarding the pics above I would say it is in the neighborhood of 20 ppm and that is close enough for government work! It I got that reading I would bump up the CYA bit until it read around 30 or 40 ppm.

As far as how high is waist high? The important point is that the tube is not 6 inches below you eyes but at about a level of your upper arms straight down and your forarm at 90 deg. to them, which for most people would put your hand holding the tube somewhere around your navel. It's not rocket science! You just don't want to be peering right into the top of the tube like it was a microscope. Holding the tube 10 inches higher or lower than someone else is not going to change the reading by any significant amouht!

Hope this helps.

[waterbear]

Thanks for all the great responses. Ever since deciding to build the pool I've hoped for a digital chemical reader, where I dip it in the water, and it instantly gives me a digital readout of all chem levels, and/or tells me exactly how much of what to add to bring the water into balance. I wonder what such a device would cost or if it's possible to build!

I grew up with my pool owner friends' parents always doing the "strips" or the dropper test, and always felt it very subjective. What if you're color blind, or what if your strips are bad, etc...

The HAVE devices like that...they are called digital pH meters, ORP meters, Colorimeters, turbudity meters, and conductivity meters (and possibly some others). Good ones can set you back thousands of dollars. The also require standard solutions to calibrate them and some of the electrodes needs special care such as being stored wet. They are actually more work and more time consuming in the long run and won't really give you much benifit over a drop test. You don't NEED that level of accuracy to maintain your pool!

Reagents do go bad, Strips have very little precision, but electrodes go bad and batteries get weak also and if a meter is not properly calibrated (pH meters are a horror to calibrate!) then the test results won't even be as accurate as a strip! I have worked with several of these types of electronic testers over the years in laboratory settings, as an aqaurist, and as a 'pool store guy'. I use a drop based kit for my own pool and my water is perfect.

[CarlD]

Those pictures are great! But only as an example. I would NEVER estimate the CYA level based on them. Cameras pick up things the eye doesn't and may be making the CYA look lower than it is.

I have outdoor speakers on my deck. No matter HOW I look at them I cannot see the woofer and tweeter through the grill. But the pictures taken CLEARLY show them... That's an example of my point. The camera is a better "eye" than the eye.