Is my CYA low?

TurboArch

Member
Apr 9, 2016
22
Houston
So, yesterday my FC level was about 2.6ppm. I added about 3/4 gallon of 8.25% bleach (trying to get it up to around 5ppm). About 24 hours later, FC is 0. I typically supplement my bleach with tablets in a floater (in case I forget to test one day). I had 2 tablets in the floater during this time, but FC still dropped to 0??? The tablets don't seem to do anything for me. Could it be due to low stabilizer?

I had high CYA before Harvey, but now it seems on the low end. I tested it with my Taylor test kit yesterday and came up with about 30ppm (but I am a little unsure of my reading). Double checked with a test strip and now I'm more confused. Doesn't seem to match either color.

Other readings from today:
PH - 7.6
TA - 80
CH - 230

IMG_5130.jpg
 

Oly

Gold Supporter
Jun 28, 2017
2,763
Fresno, CA
Pool Size
27000
I bought those test strips kits before I had my Taylor K-2006. Trust your Taylor. My CYA is at 30ppm and my strips read just like yours, nice and confusing.

After dosing with chlorine in the evening wait an hour and test your FC. Test again in the early morning before the sun is on the water. Test again after sunset before you add any chlorine. These relative numbers will provide you with valuable information. I would take out the trichlor tablets during this time to make the test more accurate.

You must determine what your FC loss is and if it is being lost from the sun (low CYA) or from organics in your water. This simple test will help you decide.
 

TurboArch

Member
Apr 9, 2016
22
Houston
Exactly why we don't recommend test strips. There is no reason to double check a reliable test kit with unreliable test strips and it only leads to confusion.

I just can't seem to trust my eyes with the Taylor CYA test. Did the dot disappear? No wait, I think I see it... Maybe not... You know what I mean?

- - - Updated - - -

I bought those test strips kits before I had my Taylor K-2006. Trust your Taylor. My CYA is at 30ppm and my strips read just like yours, nice and confusing.

After dosing with chlorine in the evening wait an hour and test your FC. Test again in the early morning before the sun is on the water. Test again after sunset before you add any chlorine. These relative numbers will provide you with valuable information. I would take out the trichlor tablets during this time to make the test more accurate.

You must determine what your FC loss is and if it is being lost from the sun (low CYA) or from organics in your water. This simple test will help you decide.

Great idea. I'll give that a shot.
 

Oly

Gold Supporter
Jun 28, 2017
2,763
Fresno, CA
Pool Size
27000
Yes the CYA test is a bit different than the others as it involves tubidimetry. The higher the CYA the more turbid the test solution will become as it mixes with the reagent. Someone here mentioned only pouring the solution to each line then looking. I too can faintly see the dot at the 30ppm line but it is gone much above it in my Taylor vial so I round up. I lose very little FC during the day so I go by my results rather than a number. I can also use a few trichlor pucks if away from my pool for a week and not have to worry about adding 5ppm CYA. Check your FC loss during the night and day before you decide what to do.
 

setsailsoon

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TFP Guide
Oct 25, 2015
4,688
Palm City/FL
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Surface
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Chlorine
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Turbo,

Technically anything over 1 ppm loss means loss means you're consuming too much at night and is an indicator that you have an algae problem. Looks like you passed but what does your pool look like? If you have no other visible signs of algae you're OK.

As to your CYA level you're going to need to perfect the technique. I had very similar issues when I first got my test kit. Took a lot of testing and watching the online videos to get confident in the reading. Also, you can get a 50 ppm standard and use this as your guide to "how disappeared" the dot has to be. This is a great way to go. I can tell you for normal readings or lower my test strips look the same as no CYA... totally worthless.

Low CYA can cause excessive FC loss but to take it all the way to 0 in one day it's more likely you had a higher organic loading from rain runoff getting in the pool. I had a similar rapid FC loss after Irma a few days ago.

I hope this helps.

Chris

PS Get comfortable with the CYA test and don't add tablets unless your CYA is low. Liquid bleach will keep it from getting too high. If your CYA level gets high and you don't run higher FC as shown in the FC/CYA chart you're not sure pool is properly disinfected an you're flirting with algae attack.
 

Oly

Gold Supporter
Jun 28, 2017
2,763
Fresno, CA
Pool Size
27000
So, I lost 0.6 overnight. Does that sound normal?

That is a low FC loss overnight and that is good. That said, I would not let your FC get that low for proper sanitation. Assume your CYA is 30ppm so your target FC should be 4-6ppm and your minimum is 2.
When do you add chlorine? Best in the evening in my opinion. Do a 25ml FC test in the early morning before the sun is on the water. Next test again after the sun is off the water and this will determine your FC loss during the day which relates to your CYA level. When dialing in your CYA and daylight FC loss use the 25ml sample for FC as this is a bit more precise measure of FC and will help you decide which CYA level is best for your system.
 

domct203

Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
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When performing the CYA test, be sure to do it outdoors on a bright sunny day, with your back to the sun & viewing the vial at about waist level in your shadow. Mix the R-0013 & pool sample in the mixing bottle and gently shake for 15-30 seconds. Let the bottle rest for ~30 seconds, then gently shake again for 15-30 seconds. Fill the vial to the first line (100), then glance for the dot (at waist level). Don't stare or your eyes will play tricks on you. If you see the dot, fill to the next line and again glance for the dot. Continue this until you no longer see the dot when glancing, which will be your CYA level. You can pour the sample back into the mixing bottle and repeat the test with the same sample a few more times until you are comfortable with the result.

As mentioned, your FC is too low. Be sure to follow the [FC/CYA][/FC/CYA] and maintain FC target for your CYA level.
 

JarCar

Well-known member
Mar 23, 2017
95
Katy, TX
I quickly learned that test strips will screw up your test results. Taylor FTW! Also, limit the pucks for when you only need CYA boost....you don't want to drive up the CYA otherwise, you're going to be dumping a large amount of chlorine to match your high CYA requirement.
 

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