Frustrated......pool chemistry

[BoDarville]

...does temperature have any effect on the chlorine level?

Two things will consume chlorine: Organic matter and sunlight. The shorter days and lower sun angles of fall & winter mean less UV rays breaking down the chlorine. Of course, both these factors lead to cooler water. As the water temperature drops, organic activity slows down. This results in a lower chlorine demand, all other factors being equal. My chlorine usage has dropped by about 2/3 since August. A good analogy is putting meat in the refrigerator vs. storing it on the counter - it will last longer in the fridge than if you store it on the counter. The cooler temps of the fridge slow microbial activity but it doesn't kill it. At some point even meat in the fridge will spoil after a given amount of time. It will just take longer for this to occur than if you left it on the counter.

I didn't have all this trouble this summer----was it because the pool was open and the sun was shining and it was hot?

Quite possibly. It seems like you may have had your SWG set properly for the warmer water and swimmer load in the summer. Although you will need to still keep an eye on the FC level as the water cools, you will likely need to reduce the pump run time or lower the FC output of your SWG or both so that FC does not get so high, as jblizzle stated.

Take a deeeeeeeep breath. Repeat after me: I can take charge of my pool chemistry and laugh in the face of pool stores from now on!

Good words to live by when it comes to pool maintenance. Suggest spending time reading the articles in Pool School during the winter. If you do, next year will be a breeze!

 

[UnderWaterVanya]

Is there anyway to check the pH and Alkalinity when the chlorine level is still too high(19)? I have been checking at least the chlorine level daily and it does seem to go up and down. The SWG is off. The cover is off most of the time, but we are expecting a lot of wind in the next 48 hours, so we have closed it to keep leaves, etc. out of the pool. Chlorine level seems to go up when the cover is on (even if I check it hours after opening the cover). Also, does temperature have any effect on the chlorine level? Anyway, since the chlorine level is still too high I can't get an accurate pH and Alkalinity check. As these two seemed to be going up steadily, yesterday I did add 1.5 pints of muriatic acid. There was a slightly decrease in the alkalinity, (now 130 so still too high, it was 150). No affect on the pH (I am getting 7.8, but according to acid demand test on the Kem-tek 5 way test it wants me to add 4 pints of acid----which of course, I am not going to do).....but we are still wanting to use the pool at Thanksgiving and I am trying to get the Chemistry right. I didn't have all this trouble this summer----was it because the pool was open and the sun was shining and it was hot?

pH actually does go up some when shocking - and then it goes down by the time the FC drops back to normal. But more importantly - the test is completely unreliable at high FC levels - the dye turns purple very quickly and doesn't read correctly at all. The only thing you could try is to get a sample and dump some chlorine neutralizer (sodium thiosulfate is one option) into it but this too impacts the pH reading (making it appear higher than normal) so it's not generally worth doing.

The cover - if opaque - is going to virtually stop your chlorine loss from the sun. Expect 3ppm per day to drop to 0.2ppm per day. The same applies per hour - so if you lost 0.4ppm per hour of direct sun before, now you will lose 0.03 or something like that. The numbers are just estimates based on other posts but your mileage could vary quite a bit.

 

[Bama Rambler]

IF the swg is completely off your FC will come down. I'd check to make sure it's completely off and not just turned down to the lowest setting, as that may not be completely off.

You can test and adjust the TA with the FC high it's just that you won't really know what the pH is.

As a last resort you could use sodium thiosulfate or hydrogen peroxide to bring the FC down but it's better to let time solve it.