Disappearing CYA

[ke263565]

hi there - been a member for 2 years or so - did the pool school - bought the tf-100 test kit or whatever it is.

I use liquid chlorine and have had pretty good success the last 2 years.

Now my question, is my CYA levels. I live in Florida with intense heat all day 90 degrees + and complete sunlight all day and it rains pretty much every day - no screen. I just cut a tree down which gives my pool about 8 hours more sunlight. I have had trouble keeping my CYA up to a normal 30-50 level. I've heard some people do even higher for Florida pools maybe 50-70. I've had issues in the past where I've had CYA way to high and had to refill because my chlorine was ineffective. So now I'm cautious with it. BUT now i cant keep the levels at a reasonable amount - it literally will get to 40-50 and within two weeks be 10 or zero. I'm going through tons of the stuff. I've tried super shocking to off-the-chart levels to kill any ammonia or whatever it is that helps the CYA not breakdown as fast. I'll have a 30 CYA and a 5-7 FC 0 CC test and then a week later, 0 FC and 0 CYA.

Maybe its just the intense weather making my pool hard to keep up wtih? I havent had any problems with algae (yet) but i've gone through a frog infested green swamp before. Any suggestions? I cant find any posts on fast dissappearing CYA - some people only deal with it a few times a season if that.

 

[JasonLion]

That sounds like there is a lot of water replacement going on. This most often happens when there is an autofill system masking a leak. It is also remotely possible to lose CYA if FC has fallen to zero for at least a day, though that is way less likely.

 

[ke263565]

I don't have an auto-fill system and I just re-piped my pool pump a few months ago. I have little to no air leaks. I'm wondering if i'm just not adding enough CYA - i don't actually know a good way to add it other than throwing a sock in and waiting a day or two. Maybe I'm just not putting enough in and getting an inaccurate reading. I use the test tube-black dot thing so its somewhat subjective.

We do get a ton of rain - sometimes my pool will get an inch or two of rain a week then slowly evaporate, etc.

If i am truly at zero or low (5, 10etc), i'll have to get formula to see how much to add. I know too much means drain & refill and I've been there twice. And I know too little doesn't do anything and i go through a billion gallons of chlorine. I just did the calculator and it says to add 50-60 oz of stabilizer. I usually will only add a big tube-sock full. I've never added that much at one time so maybe i'm not losing it, maybe i just never had any.

I know its best to add it increments as to not over do it - How long should i wait to measure? a day or two?

 

[wayner]

If you figure out what is going please keep us posted - I am having the same problem although I live in a different climate region - see this thread: http://www.troublefreepool.com/threads/80300-Keep-needing-to-add-CYA-why-would-this-be

 

[BoDarville]

How long should i wait to measure? a day or two?

I would wait about a week after a CYA addition before re-testing it. However from a chlorine dosing standpoint, I would adjust the FC dosage according to the targeted CYA level 24 hours after adding the CYA. For example, let's say you started with a CYA of 30 ppm and you added an additional amount of CYA to reach a target level of 40 ppm. After 24 hours of adding the CYA, adjust your FC dosage as though the pool is at a CYA of 40 ppm. But still wait a week before retesting CYA.

After ruling out a leak/autofill situation, the testing process may be the cause of the fluctuation you are seeing. The CYA test is the most subjective of the tests that we recommend. I would suggest looking at post # 8 in this thread which provides additional instructions on CYA testing: Extended Test Kit Directions. Since lighting is critical when doing this test, one of the things that has worked well for me is that I always perform this test in the late-morning to early-afternoon hours on a bright sunny day so that the lighting level is consistent. I always get consistent results.