Degradation of Cyanuric Acid (CYA)

[toofast]

I'm not sure if this is the correct thread but the title sure hits it...

for the past 3 years I end the winter with 60 parts per million to cya

I use the trouble-free pool method for opening and closing and everything else straight bleach. nothing else.

yet every spring my cya is back to nearly zero....

I've tried reviewing all the threads but has there been any update on this phenomena over the years?

 

[Newdude]

yet every spring my cya is back to nearly zero

You lose a few ppm per month to degradation. It's not noticeable during the season but adds up when you walk away from the pool for 6 to 8 months.

Then your mesh cover lets rain dilute it further. You get about 3 ft a year in northern Ohio, plus any melted snow.

 

[HermanTX]

Do you mix the water before taking a sample? Rain water on top can be zero CYA while the pool water you started with may have some CYA.
CYA can degrade over time - it is a slow process.
maybe @Newdude has some thoughts.

 

[Newdude]

maybe @Newdude has some thoughts.

Already Marty'd ya.

 

[toofast]

All righty thank you and yes I mix up the water. the pool's been running for a few weeks but it makes sense with the degradation and the rain blah blah blah

thanks,

 

[JoyfulNoise]

There’s bacteria that will convert CYA to other compounds for energy and not always convert it to ammonia. But it’s more than likely that dilution from winter precipitation lowers it the most dramatically.

 

[sduda210]

I test the water in October before I close. I usually have 50 ppm CYA at the end of the season. I lower the water to below the returns and allow it to fill with rain over the winter. With the combination of dilution and degradation I open the pool in late April with less than 20 ppm. I see it as a benefit since I always open with bringing the water up to SLAM level. The lower the CYA, the lower the CYA level.