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Thread: Chlorine (and effects of sunlight/shade)

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    18Wheeler's Avatar
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    Question Chlorine (and effects of sunlight/shade)

    Hi All,

    Though I am a new member here, I have been frequenting the site and forum since I acquired my 33,000 in ground concrete pool last July.

    I have a question about chlorine and sunlight/shade. My question is this:

    I know it is always recommended to shock/add chlorine at night or in the evening. I am curious if anyone has any insight on adding chlorine once the pool is in full shade. My pool is pretty close to my 2 story brick house, so full shade is around 5:30PM this time of year. Assuming shade is better than full sun as a time to shock/add chlorine, is there an advantage to still wait until dark? (No one would be using the pool when I shock either). For what it is worth, I use liquid chlorine (currently Menard's 12.5%). I also recently floc'ed the pool since I have no main drain (only one skimmer and one return) and had great results after vacuuming this morning, so at this point, I am just trying to stabilize levels/etc. So far so good. I always appreciate the good advice and thank you all in advance for any input on this topic.

    - pic of my pool attached

    Cheers!
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    domct203's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Hello and welcome to the forum.

    If you've been lurking here for months I'm sure you realize that we never recommend shocking the pool on a regular basis.

    I usually add my chlorine in the evening as it is convenient for me (after work). I suppose that the secondary benefit is less time exposure to UV from the sun, but with the proper CYA level that is minimal.

    What is more important than when, is how much. In other words, as long as you maintain the proper FC/CYA ratio it really doesn't matter when you add chlorine, except that being consistent and regular with your FC additions is key.

    Nice to have you with us, thanks for posting.


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    Richard320's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    I don't think it really matters on a day-to-day basis. For easy math, let's say your minimum FC is 4 and your daily usage is 2. You add at 6 PM. You are at 6. At 6 AM you are still at 6. At noon, probably 5. At 6, 4. And the cycle starts again. Or... you add at 6 AM. At noon you're at 5, at 6 PM you're down to 4. At 6 AM you're still at 4. What's the difference? You never dipped below minimum.

    If you're battling algae and the CYA level is real low, then you may gain some advantage by chlorinating in the dark. But you'd be adding every couple hours anyway during a SLAM anyway, so again nothing is really gained. Setting your alarm to wake you up in the middle of the night to stumble out and replenish the chlorine would probably help if the pool is a real sludgepond, but only for the first day or two.
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    18Wheeler's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Thank you, domct203. Yes, I have read that too much shocking is not advised before. Currently I am at the end of a battle with algae and trying to get the water cleared up, so I am adding liquid chlorine as needed until it maintains. My CYA is a bit low, but not dramatically (just a cpl points below 30). I am going to read up on getting a steady holding FC level now. That is something I need to have a good grip on heading into this summer. Much appreciated.



    Quote Originally Posted by domct203 View Post
    Hello and welcome to the forum.

    If you've been lurking here for months I'm sure you realize that we never recommend shocking the pool on a regular basis.

    I usually add my chlorine in the evening as it is convenient for me (after work). I suppose that the secondary benefit is less time exposure to UV from the sun, but with the proper CYA level that is minimal.

    What is more important than when, is how much. In other words, as long as you maintain the proper FC/CYA ratio it really doesn't matter when you add chlorine, except that being consistent and regular with your FC additions is key.

    Nice to have you with us, thanks for posting.


    Sent from my iPhone using Tapatalk

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    18Wheeler's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Thanks Richard320. I am (thankfully seeing blue water - a little chalky/cloudy albeit, but so much better than what it was just a day ago.) If it is one thing I have learned about swimming pools - it's that patience is a virtue. At my previous home, I owned a spa...such a breeze maintaining compared to a 33,000 gal pool, but I am enjoying learning as I go!

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    Re: Chlorine (and effects of sunlight/shade)

    18Wheeler,

    If you don't mind me asking, what are the dimensions of your pool, including depth? I saw you mention your pool is 33,000 gallons, but I'm just not seeing that, unless it's very deep. I'm just wondering as I just went through determining my pool size (+/- 12,000 gal) and yours doesn't appear to be much bigger than mine.
    12k gal. , white plaster, 1HP Century pump, Pentair Clean and Clear cartridge filter, Polaris 280 pressure side cleaner w/ 3/4HP booster pump. Built - 2011(est.) / Rosenberg, TX

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    Mod Squad jblizzle's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Welcome to TFP!!!

    I agree there is no way that is 33k gallons unless it is 10+ feet deep
    I would guess closer to 13k
    Jason, TFP Moderator
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    18Wheeler's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Hey guys, Thanks, you know, I guess I never really thought about it, but just went along with the size mentioned on the home inspection report. It is about 10 feet deep on one end to the middle. I recall my pool guy saying he thought it was a little less (I believe he thought more like 25000). I will measure it tomorrow and post the dimensions. It is a buckeye pool from what I have been told. It was built in the 80's I believe. It has a diving board, but I took it down because we are replacing it. Thx for mentioning this. I would like to know if it is a different gallon amount for sure! I will report back sometime tomorrow.

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    Mod Squad jblizzle's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Try to measure the depth. We have a board and I think it is only 8.5 feet in a small section. Likely the board would be be allowed if my pool was built today.
    Jason, TFP Moderator
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    18Wheeler's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    OK all, here are my measurements (tried to do the best I could). Let me know what you think! Were they way off in the size? (see pic attached)

    It does measure a few inches above 9 feet in the very middle (I am guessing 9 feet, 4 inches) At the stairs end it starts at 3 feet and gently slopes to 9 feet. On the diving board end it slopes up quickly to more like 5 feet. The pool has a ridge that goes all the way around about 2 feet into the water. Hoping to be able to see to the bottom soon (wish I had a main drain, but may stick my vacuum and turn it upside down to help filter the bottom stub that I can't get through the skimmer.)

    --------
    Sorry guys, I tried to update the pic and was having real headaches trying to re-attach...here you go....
    buckeye-pool.jpg
    Last edited by 18Wheeler; 04-25-2017 at 12:29 PM. Reason: mistake on pic

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    Re: Chlorine (and effects of sunlight/shade)

    Well I guess they're not that far off after all. Using an average depth of 6ft. I ended up with 29,700 gallons. I guess the depth did it.
    12k gal. , white plaster, 1HP Century pump, Pentair Clean and Clear cartridge filter, Polaris 280 pressure side cleaner w/ 3/4HP booster pump. Built - 2011(est.) / Rosenberg, TX

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    18Wheeler's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    That is more like what my repair guy thought. He really though 33,000 was a bit high. I would have to agree after taking these measurements.

    Just had our first swim today. Cold water!

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    Mod Squad jblizzle's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    Interesting. pictures just must have been deceiving with the size. I might guess that it's still a little less than 30k but as you test and adjust your Chemistry levels that you should be able to dial in on something a little closer.
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    Patrick_B's Avatar
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    Re: Chlorine (and effects of sunlight/shade)

    I have to agree on the deception. My first thought was no way! The first picture makes it look smaller for sure.
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