CYA Disappearing....

[1buccaneer]

I thought cyanuric acid stayed in the pool water but I had my cyanuric acid at 50 and now it's near zero????
My latest readings for my swg pool is:
FC - 1.5
PH - 7.4
TA - 40
CH - 70
CYA - 0
Salt - 2740

 

[Texas Splash]

That is true, unless your FC dropped so low that ammonia began to take over and consume the CYA. I would offer the following recommendations for you to implement right away based on those readings:
- Use the Poolmath calculator to increase TA to about 60.
- Use regular bleach to increase FC to 10. Test to see if it holds between 5-10 after 10 minutes. If it does, then add stabilizer for a CYA target of 30 and monitor. If your FC drops to 4 or below during that 10-min test, increase FC right away and continue that process until it does hold better for 10 minutes.

If your water is cloudy or displays any signs of algae, then once you've confirmed the FC is holding after 10 minutes go right into a TFP "SLAM" (link below). If you have any doubt about algae, perform an overnight (OCLT) test to confirm the presence of algae. Make sure the SWG is OFF during the OCLT. Hope that helps.

Pool School - Perform the Overnight FC Loss Test (OCLT)

 

[pooldv]

Yes, it is rare but possible when FC drops below normal for bacteria to grow that will consume CYA. It is important to keep FC above minimum at all times to keep the pool safe, sanitary and bacteria free. [FC/CYA][/FC/CYA]

 

[Dz7]

Is it possible you have a leak by any chance? Your other parameters are pretty low as well...apart from salt and pH. Calcium doesn't really matter though with vinyl.