CYA Burn Off From SLAM?

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kevtheo1191

Member
Jun 30, 2022
16
Southern Illinois
Pool Size
30000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I'm in the process of my SLAM, my CYA was around 70 when I started so was doing my SLAM based off of that. Fast forward to 4 days in and I go to measure CYA today and it is coming up as 0. I did a bench test with a gallon of water and measured out a miniscule amount of CYA to mix in at the correct ratio and the test does come out cloudy.

Can CYA burn off from an excessive amount of liquid shock? All the things I've read in the past say CYA only leaves when you replace pool water but I've only backwashed 2 or 3 times. Not nearly enough water exchanged to drop to 0.

Thoughts?
 
I assume you've measured CYA before; but to confirm, you're mixing pool water 50/50 with the CYA reagent, then measuring in the graduated tube? It's not unheard of for people to goof and test only pool water, or all CYA reagent.
 
reggiehammond said:
I assume you've measured CYA before; but to confirm, you're mixing pool water 50/50 with the CYA reagent, then measuring in the graduated tube? It's not unheard of for people to goof and test only pool water, or all CYA reagent.
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Correct, 50/50 mix. That's why I went back and did a test with 1 gallon of water to make sure my reagent wasn't bad.

My guess is it must have been ammonia, because I've never seen CYA disappear that quickly. Pool was running with the SWG off for 1-6 days and went completely green and grew algae in that short of time.
 
Ammonia is more typical of a pool that's been sitting over winter; not something that happens rather instantly to a pool that's being maintained.

Ammonia would destroy CYA, but also would eat FC from Slam levels to zero in less than an hour.
 
kevtheo1191 said:
I guess another question would be, could enough people have potentially peed in the pool the day before for it to go green in a day if I wasn't home to shock it?
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No - algae was likely already present due to insufficient FC. FC/CYA Levels
You actually have algae growing quite a bit before you see it.

Do you have a FAS-DPD test for chlorine? I see you list a K-2005 test kit which doesn't have the right chlorine test to see levels accurately.
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reggiehammond said:
No - algae was likely already present due to insufficient FC. FC/CYA Levels
You actually have algae growing quite a bit before you see it.

Do you have a FAS-DPD test for chlorine? I see you list a K-2005 test kit which doesn't have the right chlorine test to see levels accurately.
Test Kits Compared
Pool Care Basics
Click to expand...
Problem must have happened right after I left for my work trip then. Was about 6 days of no chlorine and blowing air mixed with water from a stuck weir door which I'm sure accelerated the problem.

Just got a FAS-DPD in the mail today which is how I measured the 11.5 FC earlier. I started the SLAM without in hopes I could get things rolling before the kit came in.
 
If your FC levels are maintaining fairly well, that'd be really hard if the water had 0 CYA.
I would expect that you could start the day at FC 8 and end at 0 with no CYA and algae.
 

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reggiehammond said:
If your FC levels are maintaining fairly well, that'd be really hard if the water had 0 CYA.
I would expect that you could start the day at FC 8 and end at 0 with no CYA and algae.
Click to expand...
Will find out shortly. Plan to do the overnight loss test to confirm whether algae has been killed off
 
Confirmed I had no CYA in the pool, wild considering I was at 80 before. CC is at 0.5 so continuing to hold FC at or above SLAM and added some CYA to get to me to 30-40 for the time being until the cloudiness goes away
 
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