Massive Drop in Salt and CYA - What Should I believe?

[swimspaguyy11]

Hi all, so last year when I was brand new to my pool everyone here was extremely helpful in getting me on my feet. I had a persistent issue with high CYA (110) and I took the advice of members here and installed a SWG and everything worked out great.

This year I did the opening myself and everything is going well except my CYA some how went from 110 to 40 and the salt went from 3000 to 1200. I did not do a major drain down of my pool at closing, however, I did have to drain about a foot of water frrom the pool twice this winter, and then I did another foot in the spring (accidently did more than I wanted because I unplugged the pump but it had a siphon and it drained slowly all night without me realizing). I added back about 9 inches of water when I opened.

The issue is, my Circupool SWG is telling me my salt is 3400 but using the TFP-100 salt test I get around 2400. Based on the pool math calculator, the 8 bags I added should have been enough to get me to 3000ppm but I am not 100% certain the gallons of my pool. Also, my salt test kit bottle #1 says best by 4-2023, bottle #2 is unreadable or missing a BB, so I dont know if that can play a role. (I thought I bought the kit mid summer last year).

It seems a huge drop for not a huge amount of water change. I really dont think I changed more than half of my pools water, that is why I am leaning towards believing the SWG salinity reading. I alsso don't want to add CYA and get back into the high CYA isssue I had last year if the reading is wrong. I am at 40 and pool math is recommending 60 for a salt pool. I struggle to do the CYA test, i keep thinking i see some of the dot from like 70 to 40, maybe even a little less.

Thanks for all of your advice as always!

 

[PoolStored]

I would replace the salt reagents. My salt was near the end of the expiration period and showed low this spring. New reagents, right as rain.

It is likely that you did drain that much water. CYA also degrades over time. Trust your test kit if you have good reagents. CYA reagent is really stable, so I believe the 40.

SWG can be off +/-500. Trust your test kit to know what you have. Trust your cell if it is happy. e.g. If you salt test says 2800 and the cell says 3200 and is making chlorine, you are good. Adjust your salt level so the cell is happy and use your test to know the real value that makes it happy.

 

[RLP]

I have found that with the cya test I like to pour it slowly into the cylinder and
Let it dribble down the side of the test cylinder, and glance away periodically.

I also dump it back into the bottle and do the pour multiple times, until I get a few matching results.

 

[clambert1273]

Cya test: pour line to line just barely glancing down after each line. Don't look hard look up at sky then quick glance down then look back up. Did you visually see it in that short period? If not, whatever line you're at is the number.

 

[duraleigh]

however, I did have to drain about a foot of water frrom the pool twice this winter, and then I did another foot in the spring

If I read that right, that's 3' of water drained from a pool that likely averages 5' deep. That explains your CYA and salt loss.