My CYA drifts low, is there anything wrong with this method to raise it??

[Cody]

My CYA is currently 30....early this month it was 50. We had a couple of really heavy rain days which caused some water to be replace with rain water....after that, I've had to add during the past two weeks due to evaporation.

So, this is how I typically handle getting it back up to the 40-50 range. At times like this, I add a pound of granular shock that I bought at Wal Mart on sale...it was about $2 per pound and i have some for the house sitter to use if I leave town for an extended time. Using this shock, the CYA will creep back up, but I'll stop before it goes over 50.

Is there ANY downside to doing this? I'm a bleach guy all the way, but since I have the shock on hand i can continue to add chlorine and increase the CYA back to where I want it. Just a quick sanity check here to make sure I'm not overlooking anything.

 

[mknauss]

Sounds like a plan ---- no issues I can see.

FYI -- you do not lose CYA due to evaporation. You do get a natural degradation of about 3-5 ppm per month. And of course if you have to drain a significant amount of water.

 

[Cody]

I just meant I lose water due to evaporation, and then when I add water it lowers the overall CYA over time.....I'm assuming my tap water CYA is nill (but I've never tested it).

 

[Pool Amateur]

Yes I believe it is and I do something similar with pucks. However 50 to 30 is a huge water replacement 40% if done at one time and if done several times as in several rain storms, is even much more. Rain can dilute it a little but does not replace unless it overflows, then it needs to be tremendous amounts to get those results. Evaporation will increase CYA, but very little, and when you add it goes back to same level so there is no water replacement. Backwashing and vacuuming to waste is a water replacement. So just be sure the CYA test is accurate before you go too high.

 

[mknauss]

If you are adding water back to make up for evaporation, your CYA level does not change. The CYA stays in the water.

No CYA in tap water

 

[Cody]

HMMMMMM....I tested three times over the past two days....CYA shows to be right at 30. 30 days ago I logged 50 into the Pool Math App two times in three days. Obviously it's the hardest test to nail down. It has to be a testing issue based on what you guys are saying. I had a lot of water overflow, but no way it was even approaching 40%.

And I didn't realize the evaporation thing. I always assumed that water "with CYA" was being replaced with tap water, so the overall CYA would drop in that instance. Always something new to learn!

 

[Pool Amateur]

Well it could have been a mistake at 50 and maybe a bit more like 40. And I could see rain over flow bringing it down by 10, light conditions seems to vary the readings for me. What I have done was to buy a 50 ppm standard and I mix the 50 ppm standard pour to 50 then take my pool water in a tube side by side and fill till it looks like the standard. I have done this earlier and later in day and on cloudy day and both my wife and myself come up with the same # and it has not varied over the past several weeks, so I think that has improved my reliability. But 3 times getting 30 seems to me to say it is 30 now. And you are set up for when you go away.