How long until the sun depletes chlorine?

[PoolGate]

If I add 3 gallons of 12.5% chlorine and there is 0 CYA (24k gallons) how long would (could) it take in the full blazing sun at midday to deplete all of the chlorine? The water is crystal clear but I can not keep any chlorine in this pool. I can't get it up to any level that it will last. The last addition was at high noon and we added 3 gallons and I just tested 1 1/2 hours later and show only trace amounts of chlorine maybe .5. I know there is (was) no CYA and we had another ammonia issue but I tested 0 ammonia early this morning on our first test of the day. I just now added 5 lbs of CYA (it is all dissolved) and am about to add 5 more pounds. I am hoping this just depleted in the sun. Or at worst there is still a small amount of ammonia. Sheesh!

 

[Dirk]

It's ammonia, sun or algae, pretty much in that order. I think the ammonia and chlorine reaction is virtually instant. The sun could clear out non-stabilized chlorine in an hour or two, no problem. I think algae takes the longest, depending on how much.

If I remember right, you definitely want to clear the pool of ammonia before you add CYA. It's a little fuzzy, but I seem to recall the CYA will feed the ammonia somehow.

I'm bumping your thread so a TFP expert can find you, one that knows more about the CYA/FC/Ammonia thing...

 

[Richard320]

Looking at this chart

it appears that the half-life is about 36 minutes.

3 gallons in a pool your size puts it to 13 FC. In 36 minutes, 6.5. At 1:12 3.25 at 1:38, about 1.6 FC remains.

As you can see and as you have experienced, without CYA, you will lose all your chlorine to the sun every day.

5 lbs will only get you to about 21 CYA. It will help some, but it really ought to be about double that.

 

[PoolGate]

Looking at this chart

it appears that the half-life is about 36 minutes.

3 gallons in a pool your size puts it to 13 FC. In 36 minutes, 6.5. At 1:12 3.25 at 1:38, about 1.6 FC remains.

As you can see and as you have experienced, without CYA, you will lose all your chlorine to the sun every day.

5 lbs will only get you to about 21 CYA. It will help some, but it really ought to be about double that.

If you are right I owe you a beer! I am tired of messing with this pool! I just added another 5lbs (I am adding in 5lb increments because that is as much as both skimmers can hold in a sock). So 10lbs total will be in shortly. I know it will take some time to fully dissolve but I squeezed it all out of the sock within about 2 hours to a milky consistency. Not sure the state that makes it and how much longer to disperse in the pool and become effective. He has a DE filter and I told him not to backwash for 3-5 days. Filter has been steady on pressure for a few days and hasn't gone up at all further making me think this is just the sun now. We have a very clear sky today and he has full sun on 100% of the pool. On my last test I did come up with trace amounts of CCs like .5. So I had .5 chlorine and .5 CCs. In the morning too he did still have some chlorine from the previous day left. Not much but there was a reading.

And PoolMath says 10lbs will take me to 50. Once I get a reading and confirm that number I will go to 70 with another 4lbs. He's using up all of my "reserve" CYA I'll need another box.

 

[PoolGate]

So I just went back out an hour after squeezing the 5lbs of CYA out and to squeeze out the next 5lbs that had been soaking in the skimmers and also had put in 1 gallon of 12.5% and got the results. I am happy to say that there was 4 parts chlorine and I was already registering 30 parts CYA! That made me very happy to add my powder and actually see some pink! Not just "oh I think that is a little pink" I got a nice dark pink like I always see on my pool. And it was very surprising to already see CYA showing up on the test. This pool actually has pretty good circulation but I did not expect to go from 0 to 30 just like that. Oh forget to add just for kickers we put in 6 pucks last night they are about 75% dissolved. Not sure how much CYA that added.

 

[jblizzle]

We have found that once it is out of the sock, it shows up on the tests within a day or so.

If you just pour it into the skimmer / filter ... there is no way to know how long it will take to dissolve in the lower flow rates. Thus the recommendation to not backwash and have to wait almost a week to test. I have had a sock of CYA in the skimmer or return jet for over a week and not fully dissolve (I was not squeezing it), so I would think it might be pretty slow to dissolve in a filter.

 

[borjis]

You might already be thinking this but do test your CYA every time you add some.

I have overshot the mark a few times. Now I only add/dissolve half of what poolmath says at a time, then test.

Also check the ph as the cya will reduce ph once added.

 

[tim5055]

Oh forget to add just for kickers we put in 6 pucks last night they are about 75% dissolved. Not sure how much CYA that added.

That will add 7ppm CYA to your 29k pool

 

[PoolGate]

We have found that once it is out of the sock, it shows up on the tests within a day or so.

If you just pour it into the skimmer / filter ... there is no way to know how long it will take to dissolve in the lower flow rates. Thus the recommendation to not backwash and have to wait almost a week to test. I have had a sock of CYA in the skimmer or return jet for over a week and not fully dissolve (I was not squeezing it), so I would think it might be pretty slow to dissolve in a filter.

I squeezed after about 2 hours and squeezed all of it out. It seemed to be totally dissolved it was very milky and came easily out of the nylon filter sock. I also tested and already showed 30ish (lol - 25ish actually I guess with the dot not quite disappearing!). Also we are seeing that chlorine held it is still at a 2-3 on the test (done 8pm tonight). I have used this same method on my pool with the same results. So squeezing it out of a filter sock (I do not use a real sock) seems to greatly speed up the dissolving! I don't think anything would be stuck in the filter at all there were no grains left. I told him hold off backwashing for a few days anyway.

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That will add 7ppm CYA to your 29k pool

Thanks! 24k actually not my pool!

 

[tim5055]

24k actually not my pool!

Smaller pool, up that to 8.5ppm