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Thread: Salt not affected by sunlight?

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    Salt not affected by sunlight?

    Hello everyone,

    I just signed up and we just had our saltwater pool finished a couple of months ago and love it. I'm still trying to learn about the chemistry and figured out test strips and stuff. We've gotten some really heavy rains so I had to add some salt and it's still only at 3100ppm after 80lbs (even cleaned out the salt cell) and am wondering about salt loss.

    Anyway, here's the question and it's probably a weird one but I'm curious. I've read that the salt only leaves the pool when water is removed, splash out, or heavy rains. And I've read that the salt is converted to free chlorine and that the chlorine eventually turns back to salt. However, I've also read that you need cyanuric acid to stabilize the free chlorine so the sun doesn't eliminate the free chlorine from the pool. So, if the sun burns the free chlorine out of the pool, is that free chlorine no longer there to be able to turn back into salt? And, if so, wouldn't that reduce the salt?

    Sorry if that sounds stupid but trying to understand it all. I couldn't find that in the forum so I figured I'd ask.

    Many thanks,

    Christian

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    Mod Squad jblizzle's Avatar
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    Re: Salt not affected by sunlight?

    Welcome to TFP!!!

    The sun just breaks down the FC back to salt.

    Do you have one of the Recommended Test Kits

    Have you discovered Pool School yet? These will get you started on the road to understanding.
    ABCs of Water Chemistry
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    Casey's Avatar
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    Re: Salt not affected by sunlight?

    You need the CYA to protect the chlorine. The chlorine will be consumed by two things and that is Sun and organics. Chlorine is always being consumed. The salt, which is not consumable, generates chlorine.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Re: Salt not affected by sunlight?

    Hi Jblizzle,

    Thank you for the welcome and thank you and Casey for the responses.

    So if I'm understanding correctly, the sun doesn't actually suck the chlorine out of the pool but turns it back to salt? Wouldn't that eventually mean salt would eventually gather in non-saltwater pools? I think I need chemistry class.

    I'm definitely planning on studying the Pool School in depth as well as any Youtube videos I can find (hopefully yours!).

    I just have testing strips so I'm not sure how accurate my numbers are but I will get them tomorrow. I'm going to be getting the TF-100. I bought some soda ash, sodium bisulfate, and cyanuric acid but I'm guessing the soda ash won't be necessary for a saltwater pool. The hardness is very high according to the strips, and the chlorine, ph, and free chlorine are on the high end though everything else looked normal on the strips. I will work on my signature tomorrow and hopefully figure this out. We got such heavy rains this past week that I ended up going from 3200ppm salt to a ping pong between 2400 and 2600 and have added 80lbs of morton pool salt and still am only at 3100.

    On a fun note, I'm using the Hayward Omnilogic. Not sure if anyone else on here uses that but our pool builders said we were the first in New Orleans he's sold it to. Controlling this thing from the phone rocks.

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    Casey's Avatar
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    Re: Salt not affected by sunlight?

    The salt water generator turns it back to chlorine using the salt that is already in the pool. Salt in the pool does not dissolve on it's own unless you dilute it with water. The Sun destroys chlorine as do organics in the pool. Adding chlorine like liquid bleach adds a very small percentage of salt to non salt pools.

    You're testing strips are not reliable. The TF100 is a great kit. Get the XL and a speed stir too. You'll love that little gadget.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Re: Salt not affected by sunlight?

    Casey: when you say that "the sun destroys chlorine," do you mean that it turns it back to salt like jblizzle seems to be suggesting? I might not be explaining my original question well, but think of it this way:

    100 parts salt --> converted to 100 parts chlorine by machine --> minus 10 chlorine destroyed by sun --> remaining chlorine turns back into 90 parts salt. i.e. less salt.

    I understand that's not what actually happens, but I'm curious as to why. If the sun actually evaporates chlorine rather than turns it back into salt, then wouldn't there be less chlorine to turn back into salt and, thus, less salt?

    I also realize the only way salt comes out of the pool is heavy rains and/or taking it out (such as us constantly taking the suction vacuum out and leaving it on the patio) but there were some seriously heavy rains so I've had to add some serious salt.

    I'm definitely getting the TF100.

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    Re: Salt not affected by sunlight?

    Just posting this to test signature.
    10k gal gunite/plaster Hayward OmniLogic panel with phone app Hayward ColorLogic Lights Hayward Heater Hayward AquaRite salt chlorinator Hayward Pool Vac XL Hayward Pump Four custom swim jets with 2 Hayward pumps

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    Casey's Avatar
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    Re: Salt not affected by sunlight?

    The only way you lose salt is to dilution. That's it. There is no other way to lower salt levels. The Sun plays no role in diminishing the salt content of a swimming pool.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Mod Squad pooldv's Avatar
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    Re: Salt not affected by sunlight?

    The sun does not evaporate or destroy chlorine it oxidizes it. If it never rains and you never splash any water out of your pool then the salt level will be the same 10 years from now that it is today. No matter what your SWG is doing with or without sunshine.

    - - - Updated - - -

    Quote Originally Posted by christianday View Post
    Just posting this to test signature.
    no need to post test results in your sig, they will change often.
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    Re: Salt not affected by sunlight?

    pooldv: thank you! That makes sense. When the chlorine is oxidized, does it turn back to salt?

    will change sig.

    Thank you again
    10k gal gunite/plaster Hayward OmniLogic panel with phone app Hayward ColorLogic Lights Hayward Heater Hayward AquaRite salt chlorinator Hayward Pool Vac XL Hayward Pump Four custom swim jets with 2 Hayward pumps

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    DaninFLA's Avatar
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    Re: Salt not affected by sunlight?

    Quote Originally Posted by christianday View Post
    pooldv: thank you! That makes sense. When the chlorine is oxidized, does it turn back to salt?

    will change sig.

    Thank you again
    check out this thread: Chemistry behind chlorine salt water generators

    cliff notes: when you add salt to the pool, the molecules separate. you end up with sodium and chloride. the SWCG combines two chloride molecules to create chlorine gas. as the chlorine gas is oxidized killing algae or via the sun, it breaks back down into the two chloride molecules....back to square one

    so no, it doesn't turn back into salt, the molecules stay separate. if you dehydrated the pool, you would get the salt back
    Dan
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    Mod Squad pooldv's Avatar
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    Re: Salt not affected by sunlight?

    For laymen terms and our purposes it is a closed loop process. With no splash out or overflow we would never need to add salt to the pool again.

    I do love a chemgeek post about it, but I can't understand it.
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    Re: Salt not affected by sunlight?

    God. Just trying to find out the model of these things is insane. The labels are confusing and googling the model number of the filter machine, for example, gives me three different filters and isn't definitive. The pump is the same. I google that number and I get a square pre-filter sheet. Oy. I had no idea this was such rocket science.

    As for the salt chem, so salt is still salt if it's just sodium and not sodium chloride? I'm gonna go check out that link. This is a lot to learn.
    10k gal gunite/plaster Hayward OmniLogic panel with phone app Hayward ColorLogic Lights Hayward Heater Hayward AquaRite salt chlorinator Hayward Pool Vac XL Hayward Pump Four custom swim jets with 2 Hayward pumps

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    Re: Salt not affected by sunlight?

    The sodium part of salt doesn't participate in the chemical reactions that go to/from chlorine. It's just there for charge balance and it increases the conductivity of the water.

    So let's just focus on the chloride/chlorine side of things. You initially add salt to the pool to get to around 3000 ppm (parts per million) of salt (measured as proportional weight of sodium chloride in water) and this is so there is enough electrical conductivity and chloride ion in the water so that the saltwater chlorine generator can produce chlorine. (Full technical details in this post.)

    When the chlorine breaks down in sunlight or oxidizes an organic or ammonia it becomes chloride again. So there is no net gain or loss of chloride salt from the pool. Now there is a small amount of chlorine that can outgas and a small amount that can combine with an organic and not oxidize it, but most of the loss of salt in a pool comes from water dilution via splash-out, carry-out, rain overflow, and backwashing.
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    Mod Squad pooldv's Avatar
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    Re: Salt not affected by sunlight?

    Thanks CG, I made some progress on that one!
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