Dissapearing CYA

[hopkiba]

Here are my test results taken today using my K-2006-Salt kit.

FC 13.0 My generator that runs 12 hrs/day went for 80% to 40% with no significant reduction is FC levels. How come?
CC 0
PH 7.6 Stays steady
TA 65 Stays steady
CH 40
CYA 0 It was 70 about 3 weeks ago after adding stabilizer. Strips confirm that it is low. Why would it fall to 0?
Salt 3000. Was 3600 about a month ago.

We have had a lot of rain that could explain salt and CYA going down. When I was using tablets, I had to drain 1/2 the pool every year because CYA was high. Do salt systems somehow consume stabilizer?

 

[Donldson]

If your salt readings are anything to go by, you've replaced 20% of your water in the past month. Have you gotten a lot of rain? Like, two feet of rain in that time?

 

[hopkiba]

If your salt readings are anything to go by, you've replaced 20% of your water in the past month. Have you gotten a lot of rain? Like, two feet of rain in that time?

 

[hopkiba]

No any where that much.

 

[djdonte]

You said you confirmed the CYA with strips, but did what are you doing all this testing with?

 

[hopkiba]

Testing was done with a Taylor K-2006-Salt kit.

 

[IceShadow]

Seems like a mystery. There are bacteria that can eat CYA and turn it to ammonia, but if that were the case the ammonia would burn up your FC and you wouldn't have any of that in the pool either. Did you have any points in the past 3 weeks where you had to put a ton of chlorine in the pool to get levels to register?

 

[hopkiba]

Nothing unusual with chlorine usage. Started out with liquid chlorine but have been on salt since mid April.

Just got back from the Pool Store and they said that it was at 30. My target CYA is 70. Will add 4 lbs or so and see where I end up

 

[Randrx2]

I have had some weird CYA losses, but I think I may have figured it out, I hope!

Make sure you are doing the test right. I highly recommend getting the 50ppm CYA calibration standard: R-7065 CYA Standard 50 ppm (2 ounces). This will help you confirm your test conditions.

Also, having the sun behind you while performing the test makes a difference. I did the test this way and then looked at same sample in the shade, then indoors. I was amazed at the difference in the dot in the different lighting conditions.

There is some error in the testing. So what you may think is the number can be 10 ppm off.

You can naturally lose 5-10 ppm per month of CYA. Your loss is drastic though, so this may not account for all the loss.

If you clean your filter too soon after adding CYA, you can lose some.

Last, but not least, look for water leaks.

Here is some reasoning: Let’s just say your first test had some error. So call that test actually 60ppm. Then, assume there was some natural loss, down to 50ppm. Then assume the rain and drain dropped you down to 40 ppm. So you may not be as far off as you think.

I hope that helps.

 

[Randrx2]

Also, when you add the CYA. Add it 1 lb. at a time max (or the amount needed to raise 10ppm per PoolMath). Then test after 24-48 hours to see if you get the expected rise. You do not want to overshoot.

 

[gregsfc]

I'm 75 miles due north if a crow flew it in Cookeville, and while we haven't had two feet of rain here on the Highland Rim, we've probably had one foot in three weeks. If you combine test reading inconsistencies, which are hard for humans to eliminate, and half the rain propurted that would cause a large loss in the cya level, that could be an explanation. My pool has been at the top of the skimmer since two days after opening. Started right about the correct level. All due to inches upon inches of rain every week that has far out paced evaporation so far this year.

 

[hopkiba]

I think I found the problem. The pool store measured 30 and I added 2.5 lbs of Stabilizer. I then tested but saw no clouding of the test sample. The R-0013 was from a large bottle I bought a few years back. I had calibrated against a fresh reagent from a new kit and both tests agreed.

I decided to buy a new bottle and my CYA is now reading at about 70. looks like my old reagent died all of a sudden!

 

[Randrx2]

I think I found the problem. The pool store measured 30 and I added 2.5 lbs of Stabilizer. I then tested but saw no clouding of the test sample. The R-0013 was from a large bottle I bought a few years back. I had calibrated against a fresh reagent from a new kit and both tests agreed.

I decided to buy a new bottle and my CYA is now reading at about 70. looks like my old reagent died all of a sudden!

Thanks for the follow up! It is nice when a problem is solved and you are willing to share. This helps us all.

 

[mknauss]

looks like my old reagent died all of a sudden!

That is one of the most stable reagents. Unless you let it freeze.