Consistently losing CYA

[cale42]

The title about sums it up. I have the opposite problem of so many.. I can't keep CYA consistently high enough. I first started noticing it last year. It became more pronounced at the beginning of this year. Pool has been open about 10 days.. tested CYA right around 30 on opening(Taylor R-0013 test). Today was surprised to find chlorine at zero and I tested the CYA and it was essentially at zero.

I do struggle with big water loss. I lose between 100-200 gallons a day out of a 20,000 foot pool. Live in the Midwest.. pool is 16x36.. so big surface area, lots of sun, very breezy, no cover(this one will be remedied soon).

In the past 10 days since opening we have also done a serious vacuum to waste, added water to fill on opening and have had three torrential rainstorms. But still seems odd to find CYA at zero.

Any thoughts or ideas on what is causing this? I didn't think anything could really cause CYA to dissapear.. and even figuring maybe I've added 5000 gallons of fresh water in 10 days it shouldn't have gone down this much. Or is the problem simply I'm testing wrong? I suppose that is possible.. but my struggle to maintain chlorine indicates a lack of CYA.

Ultimately I'm guessing I might have to develop a hybrid routine of using both liquid chlorine supplemented with dichlor and trichlor. Or maybe a solar cover will make more difference than I think. But is there anything I'm missing here?

Thanks,
Chris

 

[Donldson]

Evaporation does not cause CYA loss. Sounds like you have a leak if you are loosing that much water every day.

 

[mknauss]

CYA does not leave the pool due to evaporation. It does when you vac to waste.

When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....

 

[cale42]

I'm also concerned about a leak. But it's borderline. So I haven't pursued it too aggressively yet. A "normal" 1/4" evaporation a day is 80 gallons for me.

So I was doing a bit more reading here after posting. Do I understand correctly that when free chlorine goes to zero algae can eat CYA and turn it to ammonia? Meaning if my pool was closed for 6 months it's highly unlikely there was any CYA whatsoever in it when I opened up. So I probably performed the test poorly then?

Thanks for the testing tips.. I will give them a shot!

 

[mknauss]

It is not automatic that your pool gets the bacteria over winter to consume the CYA and generate ammonia. Most times low CYA at opening is just from water displacement due to snow melt, rain, etc.

 

[borjis]

Ya it doesn't happen to every pool. It's a fairly rare occurance and more often then not the CYA does a complete conversion to harmless Nitrogen.
It's when the process is somehow interrupted that you end up with Ammonia.

I always lose a bit of CYA over winter.
I maintain 50 over the swim season, usually open to 30 on March first.

But I lose 20ppm between that opening day and July 1st. Every year.
Somehow rain or no rain it just goes down 20ppm each June.
Not scientific by any means, but the only variable is my neighbor's red
pine dumps a ton of pollen right in my pool in late may and all of June.

So I up it back to 50 and it sits there until closing in late sept early oct.
wash\rinse\repeat--going on 4 years of that.