Does aerating increase the loss of FC

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M

mokabb

0
Jun 10, 2009
60
Northern Philly Burbs
I was just curious...

Today, I have been aerating after I added MA (lowering TA). It seems as though I can smell the chlorine more than usual when walking around the pool. Will I lose more than usual? Does aerating accelerate FC loss? I'll let you know tomorrow if you don't tell me the answer before then

Numbers 1 hour after latest MA addition
pH 7.2
TA 85
CYA 70
FC 8.5
CC 0
clear pool...
 
It should. I know in aquariums we used to say that if you aerated the tap water for 24 hours you would drive off the chlorine. But, if it has chloramine instead, you'd have to aerate a month to drive off the chlorine before it was safe to add to a fish tank.

Anona, who learned that keeping fish was really about keeping water
 
It would theoretically accelerate some chlorine outgassing, but it's a lot slower than in an aquarium because the CYA in the water significantly lowers the active chlorine (hypochlorous acid) concentration that is mostly what outgasses. With the recommended levels on this forum, the active chlorine is roughly equivalent to around 0.1 ppm FC with no CYA which is quite a bit lower than what is outgassed from aquariums. If you notice a greater FC drop, especially overnight (if you are still aerating overnight), let us know as that would be useful info to know.
 
chem geek said:
It would theoretically accelerate some chlorine outgassing, but it's a lot slower than in an aquarium because the CYA in the water significantly lowers the active chlorine (hypochlorous acid) concentration that is mostly what outgasses.
Click to expand...

Oh, of course.... CYA which "binds" the chlorine! I didn't consider that.

Anona, still the novice
 
Mokabb...you did wait at least 30 minutes after adding bleach to add MA right? I made this mistake at first of adding bleach and then two minutes later, lowered my PH from 7.6 to 7 and almost fell over from the chlorine gas smell.

If your in the process of lowering TA and you need to adjust your FC...makes sure to leave at least 30 mins between bleach and MA additions.
 
Thanks for the tip, dman. I didn't add them back to back, but I'll make sure that I don't in the future. I tend to broadcast the acid around the perimeter, with ~ 1/2 in front of the returns to the pool. I've been tending to put the chlorine in the skimmer. So, there probably wouldn't be much of a reaction regardless if I put them into the pool closer in time.
 
chem geek said:
... If you notice a greater FC drop, especially overnight (if you are still aerating overnight), let us know as that would be useful info to know.
Click to expand...

I've been using the bleach now for my chlorine source for ~ 2-3 weeks (after I finished the shocking process) as I am a recent puck convert. The FC has not been dropping more than .5 overnight, though it has been averaging ~2 ppm loss over 24 hours. Cover usually has been on. Swimmers every day to every third day.
 
Thanks. That's pretty much what I expected, but it's good to get some confirmation.

Your 2 ppm FC per day loss is a little higher than normal when using a pool cover unless the cover isn't opaque to UV. Is it a clear cover, a light blue cover, a dark blue cover, or something else?
 
The cover is dark blue. It seemed that I am losing more chlorine than the average posted here. There are days that I lose closer to 3 ppm, even without taking the cover off and without swimmers in the day. I just figured it was normal variation. I have been adding on average 4-5 ppm every 2 days.
 

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Wow. With a 0.5 ppm FC drop overnight but a 2-3 drop over 24 hours you are certainly losing at least some to sunlight in spite of your blue cover. I guess it lets some UV through. That's surprising, but good to know. My cover is pretty opaque though not absolutely completely dark to all light. It does seem to keep out nearly all of the UV since I notice no difference in overnight vs. daytime FC drop (per hour).
 
Does my high CYA level help explain a higher than average FC loss? I know that with a high CYA (recently measured to 70-80), I have to keep a high FC level to maintain a high "effective" chlorine level. What else is bad about a high CYA level except for needing to keep a high FC? If I decreased the CYA to 40, would it impact on my loss. I just have a "thing" about wasting water unless I have to ( a throw back to the 70s ). I want to try to wait until I drain (closing )and refill (opening next year) to try to deal with the high CYA.
 
In theory, the higher CYA level even with a proportionately higher FC level should have a lower chlorine loss due to the shielding effect of the CYA on the lower depths of water. That's what most people find. So that doesn't explain your higher loss and I'm at a loss for an explanation unless the cover is letting in UV light.
 
mokabb said:
Does my high CYA level help explain a higher than average FC loss? I know that with a high CYA (recently measured to 70-80), I have to keep a high FC level to maintain a high "effective" chlorine level. What else is bad about a high CYA level except for needing to keep a high FC? If I decreased the CYA to 40, would it impact on my loss. I just have a "thing" about wasting water unless I have to ( a throw back to the 70s ). I want to try to wait until I drain (closing )and refill (opening next year) to try to deal with the high CYA.
Click to expand...

The really bad thing about high CYA levels besides needing to maintain high FC levels becomes readily apparent if you have to shock your pool. Go check out your shock level in the pool calc. For a big pool, it tends to add up to ginormous amounts of chlorine. :shock:

edit: I decided to go look at the pool calc myself, just for grins. For your size pool and CYA=80, your shock level is 21. To go from FC=8 to FC=21 would be 674 oz of 6% bleach, or a little over 5 1/4 gallons of bleach for the intial dose, and depending on how bad the algae is, you could be adding similar sized doses repeatedly. :shock: :shock:
 
I have a new dk blue solar cover, and the first two days of use I lost NO FC (no swimmers either, pool stayed covered.) I think in general when it's covered/not in use the pool loses less than 1ppm for 24 hours. My CYA is 40-50 (haven't tested lately). When the cover is off and I have swimmers I lose probably 2-3ppm during the day (varies with bather load).

I'm wondering if you have organics lurking in your cover? You shouldn't be losing 3ppm during the day with the cover on and no swimmers.
 
Thanks for the replies. Yes, I had to shock a few weeks ago and kept it in the 20s for several days. WOW, that was a lot of bleach.

I also wonder if there was some "stuff" in the cover. Of some interest is that I think that I only lost ~1 ppm over the past 48 hours. The cover has been on, it rained all day yesterday, and there was minimal swimming today only. This is the first time that I have not needed to add bleach after 48 hours since I started BBB last month. Maybe, I finally got there somehow. I'll let you know if this nice trend continues.

Perhaps there were some organics in the cover which finally got cleaned off. Also, silly me, my air pockets are up instead of down, so maybe some stuff was getting stuck there.

Of note, I finally found an "easy" method of using the cover on my free from pool. No longer is it a HUGE PIA.
 
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