Reminder to check your CYA weekly

GenericHbomb

Well-known member
Oct 3, 2015
72
Rochester, NY
Green slime started invading my pool and I couldn't figure out why. Kept adding bleach per my daily and seemed to get worse, finally did a full test.

Somehow, which I am unsure of, as I tested fully and balanced in beginning of season, I ended up with zero CYA. I usually don't test CYA too often as it holds but learned my lesson here.
Between all the rain this year, backwashing and draining rain likely got the level way down.

Added CYA and gave it a few days to absorb and dissolve in the water.
Looks like my chlorine was probably burning off as fast as I was adding.

So lesson learned, need to check CYA weekly.

Anyway, full test. I just added some bleach about an hour ago as sun was going down.

FC 4
CYA Between 30 and 40. For purposes of slam going with 40
CC .5
TA 100
PH 7.8


Going to add 4 more jugs to the pool which should get FC up above 16 overnight and start the slamming process.
Hopefully can be done slamming by the weekend.
Lesson learned.
 

Natrix

Member
Jan 7, 2021
14
Tucson, AZ
I hate the CYA test as it's the only real subjective one and I always struggle with deciding which measurement it is closest to. I do it weekly though just to stay on top of it. Good luck with the SLAM.
 

GenericHbomb

Well-known member
Oct 3, 2015
72
Rochester, NY
I hate the CYA test as it's the only real subjective one and I always struggle with deciding which measurement it is closest to. I do it weekly though just to stay on top of it. Good luck with the SLAM.
Yea never really liked it either. I always feel like I can kind of see that black dot longer than I can. My first year doing the CYA I always concerned I was wrong. As long as you are consistent with yourself, I think that is key.
 

revitup

Gold Supporter
Bronze Supporter
Nov 30, 2019
645
Pawleys Island, SC
Pool Size
8500
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Check CYA weekly? I can’t imagine how much rain water I’d have to get to be draining enough to affect CYA that much. I think every inch of water would lower my CYA like 1%. How much do you backwash? I might twice a season for 5 minutes. Something doesn’t seem right.
 

BenB

Gold Supporter
Jul 24, 2020
269
San Jose, CA
Pool Size
19500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
Was going to post my own reminder thread but you beat me to it!

I got my CYA to 70 at the start of the season (February/March time) and since then have ignored it because CYA is supposed to stay in the water. Well, despite having a cover on pretty much the whole time except when swimming, and having minimal splash out, I retested last week for the first time since then and am now at 40-50. So I've been running high on my FC and missed out on buying CYA to make it up back when it was cheap.

No outbreaks as I was running higher than I needed to, but still annoying. Will be sure to check everything now more often, even the figures that "don't change".
 

Cody

Bronze Supporter
Aug 17, 2014
226
Prosper, TX
CYA and pH test are tough for me....the dot kid of disappears and I've been doing it long enough that I think I'm consistent...with a lot of rain mine has dropped more this year than normal as well. On the pH test, i pretty consistently think the red doesn't match ANY of them! lol
 

CraigChing

Gold Supporter
Jun 15, 2019
189
Plymouth, Minnesota
Pool Size
22000
Surface
Vinyl
Chlorine
Liquid Chlorine
A couple of points:

1. You can redo the CYA test multiple times by pouring the solution back into the mixing bottle and starting over. I do it a few times just to make sure. I do the “fill to a line and check” method as well as a “drop until I don’t see the dot” method and compare. They match for me, but I still like to check using both methods.

2. There is a 50ppm reagent you can buy and see what 50ppm CYA looks like for you. I think it’s just a “add it to the cylinder and see” reagent, I haven’t tried it yet, but I’m thinking about trying it to make sure.
 
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GenericHbomb

Well-known member
Oct 3, 2015
72
Rochester, NY
Check CYA weekly? I can’t imagine how much rain water I’d have to get to be draining enough to affect CYA that much. I think every inch of water would lower my CYA like 1%. How much do you backwash? I might twice a season for 5 minutes. Something doesn’t seem right.
I dont disagree. It has been raining almost non stop here and only thing I can think of. Before the rain came it was dry and was the complete opposite. Im in your boat where CYA was a set it and forget it type thing and I got bit. Dont know how or why it got so low.

Been backwashing to lower the pool water level as it keeps getting too high.
 

BowserB

Silver Supporter
Jul 29, 2018
648
"Old" Katy, TX
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I hate the CYA test as it's the only real subjective one and I always struggle with deciding which measurement it is closest to. I do it weekly though just to stay on top of it. Good luck with the SLAM.
+1 on this. I felt like I had it mastered until I went to SWCG and had to run higher CYA (I still don't understand why). At the higher levels the lines on the cylinder are closer and closer together. I'm thinking of using the dilution method where you double the result. There is space between the lines in the 30-50 range. That said, total loss of CYA seems impossible to me. Indeed, it sounds more like a mistake than an event--either the earlier test result was wrong or the recent one was. This could be a time when a free pool store test might be useful to see what they get. The pool stores get bad mouthed, but the Leslie's near me has had results that nearly match mine when I've done my own and then took another bottle of water to the store. It helps that I'm retired, so I can go to the store at slow times and watch the clerk do the test and then discuss differences when they show.
 

willygee

Silver Supporter
Aug 24, 2020
180
central fla
Pool Size
10000
Surface
Plaster
Chlorine
Liquid Chlorine
I still use the aqua check 7-way strips for cya and compare to pinch a Penny. They pretty much always match. TF 100 is in our future though.
 

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ghall6292

Bronze Supporter
Jun 10, 2018
142
North Central PA
Like the OP, I have been draining off tons of water this year due to excessive rainfall. In a normal year my CYA is pretty much set it and forget it, but this year I have had to boost it back up three times already. This is a good reminder for us all to test even "the things that don't change" once a week or so. It's really cool to watch a SLAM clear up the water; but to be honest, it's much cooler watching it clear up yours rather than mine. ;)

Early this spring, I purchased from TFTestkits a much skinnier cylinder for testing CYA that really saves on the amount of reagent needed to do the test. I use 5ml of pool water and 5ml of reagent placed into the normal "everything but chlorine" cylinder. Then pour this into the CYA mixing bottle and shake it up. Then pour it into the skinny CYA test cylinder. This 10ml of solution will overflow the skinny CYA test tube if you want it to.

The only drawback is that it tests from 100 to 30, not 20 as in the standard cylinder. For me, anything below 30 is panic button time anyway. Wouldn't dare to intentionally run it anywhere near 20.
 
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