Spring Opening Chemical Readings

[ssgumby]

So I just tested my water for the first time. Pool is being opened this weekend. Still winterized as of right now, I just pulled the cover back to test.

1. CYA = 0
2. FC = 0
3. TA = 30

First question, I understand FC would probably disappear, but why would the CYA vanish completely? Last year I ran CYA of 65 and FC of 5 using a SWCG. I've read tons about if CYA got too high the only way to get it down was to drain. My circumstance was I drained down about 15 inches and with precipitation I had to pump some more off a few weeks ago to get the level to where it should be. Would that amount cause all CYA to disappear?

My second question is a puzzler. Last year my TA was always over 100. I worked all summer to get it down and eventually I was right around 100. I test today and it is 30???? How the heck is that? Now I need to raise TA?

Lastly, wow is that water cold. 45 degrees! Brrrrr! My hand is numb as I type.

 

[woodyp]

Our in house team of dedicated pool scientists still can't explain why cya sometimes disappears over the winter--but it happens. My TA always drops by a bunch over the winter as well if I don't mess with it. Usually from 60ish to 30.

 

[Leebo]

Cold water does alter the cya test. Let the water come to room temp, then retest. We've also had a very "wet" winter. Was your water level higher than it was when you closed? Have you drained any pool water?

 

[ssgumby]

Cold water does alter the cya test. Let the water come to room temp, then retest. We've also had a very "wet" winter. Was your water level higher than it was when you closed? Have you drained any pool water?

Ahhh, good info. I will bring in some water and let it warm to room temp and test again.

As for water level, I drained it down about 15" when winterizing. Then had to drain a couple inches a few weeks ago to get it back to a normal level. So overall I changed about 17" of water.

 

[Leebo]

Without knowing your pool gallons.......

You could have added around 4-5k gallons of fresh water with that 17" drain/refill. Keep that in mind too.

 

[ssgumby]

So I rechecked CYA after allowing water to warm to room temp and it is till 0.

Just find it interesting that even with changing water it would drop to 0.

 

[Patrick_B]

Sometimes it happens. Seems that one of the prevailing theories is that it's consumed by bacteria and converted to ammonia.

 

[ssgumby]

Well, let me throw this theory out.

I opened my pool, and now with the pump running CYA is around 40.

Crazy, but can CYA "settle"? As in once the pool was circulating could it remix CYA and now im getting readings?

 

[pwrstrk]

Could very well be the case.

 

[duraleigh]

For accuracy, none of the tests we perform should be even attempted until the pool water has circulated for about 30 minutes or so.

 

[chem geek]

I don't think it's so much that CYA "settled" as that fresh water got added on top along with possible overflow and that diluted the CYA level in the upper layers of pool water. If you don't have circulation then you can certainly stratify the water. Basically, did a partial drain and refill with the top layers of water without mixing the bottom layers with it. Does that sound plausible?

 

[ssgumby]

I don't think it's so much that CYA "settled" as that fresh water got added on top along with possible overflow and that diluted the CYA level in the upper layers of pool water. If you don't have circulation then you can certainly stratify the water. Basically, did a partial drain and refill with the top layers of water without mixing the bottom layers with it. Does that sound plausible?

that makes perfect sense and is most likely the cause!

 

[kodiak1120]

Hi,

My pool's the same way... always zero CYA (or less than the detectable amount) when I open. No worries, I just use some chlorine floaters for the first few weeks. They help keep your FC levels high when you first shock the pool, which is helpful when opening. I usually keep my CYA on the low-side, so I can add the pucks when I'm going away or won't be around to add chlorine.

 

[duraleigh]

The last four years, my CYA opening result has been 50, <20, <20, 50. Trying to figure that out makes my head hurt.....I think the pool gods are toying with me

 

[woodyp]

I always average about 20 when I start getting levels right after winter when it starts warming up some. TA is always 20 or 30 as well.

 

[ssgumby]

A quick update. After a week of running the pump and pool warming to 56, CYA is measuring 50 and TA went to 150. Nothing added other than bleach.