Cyanuric acid levels dropping

[Toonetown]

It seems to my my CYA levels are dropping faster this year than previously. I tested on June 4th and it was at 75. I tested today and it was at 45. The pool has been used - but not a lot of splashing and not even a lot of evaporation (I had to top off my pool about 1.5 inches today…first time since the 4th when I last checked CYA).

Is this normal loss? I don’t remember it getting lowered that quickly in previous years. I have also noticed that my chlorine levels drop faster after a day of use than they did a few weeks ago (clearly because of lower CYA). Everything else in the water is very in-balance, so I’m a bit confused as to what could cause CYA to drop like this.

 

[mknauss]

Lots of UV and likely higher pool water temperatures. Both degrade CYA.
Odd you have limited evaporation. Is the pool covered?

 

[mrm1682]

I experienced the same over the last 1-2 weeks with CYA dropping. We’re entering peak sun season so only about 2 hours of shade max right now and stays this way for rest of the summer. Just added some today and will typically find myself adding again depending on heat, use, and refilling needs (depends on evaporation from heat but also how much use the pool use is).

 

[mknauss]

depends on evaporation

Evaporation does not effect CYA levels. CYA is a solid. It stays in the pool water.

 

[mrm1682]

Yes but doesn’t adding water over time affect CYA? That’s my understanding from previous reading here. Probably a very small change when adding fresh water from use but it does affect things over time I thought. Basically a dilution effect?

 

[PoolStored]

Yes but doesn’t adding water over time affect CYA? That’s my understanding from previous reading here. Probably a very small change when adding fresh water from use but it does affect things over time I thought. Basically a dilution effect?

Depends on why you are adding water.
From evaporation. No.
From backwash, removal to waste, and splashout. Sure.

 

[mrm1682]

Hmmm haven’t broken down type of water loss before like that but I guess it makes sense. Hard to tease it all out but it’s multifactorial all summer during peak use. Regardless of cause, I’ve always noticed CYA drops during this part of the summer we’re starting.

 

[mknauss]

CYA - Further Reading

www.troublefreepool.com

 

[Toonetown]

Yes - I keep it covered most of the time. The heat and sun makes sense…it recently got very hot. I am fine to monitor and just add as needed…but was just confused because I was under the impression it wasn’t as necessary to check cya levels as often as other levels like ph and chlorine. This is still less - maybe weekly instead of daily - but I was thinking checking cya monthly or once per season would be sufficient if there wasn’t a lot of splashing loss.

 

[mknauss]

Checking CYA monthly is fine. But if you see a drop in FC that is unusual, check the CYA level.