Another opening, another 0 CYA

[aseigler]

Over the winter each year my CYA level drops from normal levels to zero. Is there anything I can do to prevent this? It's not a huge deal to re-CYA once a year, but I dumped almost 20 gallons of 10.5% in the past 2 weeks before I remembered the winter CYA disappearance issue.

 

[Patrick_B]

It's very common in pools that go green over winter. Did yours?

 

[aseigler]

Not too bad this year, but it did cloud up a bit and had some green, but not swamp territory. I generally quit running weekly tests when the daily highs drop out of the 80's. I maybe burn through a quarter or less of the chlorine I use the rest of the year. Does letting the FC get super low contribute to CYA loss?

 

[Patrick_B]

Yes, and the most commonly accepted theory and explanation is that it is consumed my biologial activity. (Bacteria)

Whatever the case, you need to complete a SLAM procedure on your pool. Don't raise the Cya over 30 before you get that done.

Can you go ahead and post a full set of results before you procede?

 

[aseigler]

Right now I am looking like:

FC 4
PH 7.5
TA 90
CH 250
CYA 0
Borate 40

Water is right at 78 degrees F. My FC is pretty stable overnight but I lose almost everything during the day, unsurprisingly.

 

[Patrick_B]

Ok, Not bad.

I would increase the Cya to 30 and SLAM it. If you are comfortable with it, lower your pH to 7.3 as a target as well.

Not critical, but you won't have to worry what it is during SLAM.

SLAM SLAM SLAM till you're done.

 

[aseigler]

I have a tough time seeing the difference between 7.2 and 7.6 on the pH scale. I wish there were a more accurate test. Same thing with borates.

 

[Patrick_B]

Which pH test are you using? For those two ranges it should pretty easy with a phenol red pH test.

 

[Smykowski]

Over the winter each year my CYA level drops from normal levels to zero. Is there anything I can do to prevent this? It's not a huge deal to re-CYA once a year, but I dumped almost 20 gallons of 10.5% in the past 2 weeks before I remembered the winter CYA disappearance issue.

Our best guess for avoidance is to close the pool late in the summer when the water is cold, it must be clean and clear when you close, and your FC has to be at SLAM level. Cold clean water will slow down the rate of FC use, so that you will have FC upon opening, thus preventing anything from living in the water which will break down the CYA.

 

[zea3]

You may want to test for ammonia before adding the CYA. Ammonia is a by product of CYA degradation due to bacteria. You can get an ammonia test anywhere that sells aquarium supplies. If it shows you have ammonia, it is best to clear it before adding the CYA. Otherwise it may continue to break down the CYA you just added. You slam with bleach to get rid of the ammonia.