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Thread: Downsides to salt pools

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  1. #1
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Downsides to salt pools

    OK, I'm starting a thread to examine the downsides to a salt pool. Yes, there are many benefits and these have been talked about on other threads, but my search through various forums led me to one guy who posted some information that was correct and some that was not. But it was the correct information that got me thinking about presenting a more balanced discussion to salt pools. I am starting this thread in The China Shop because the issues are tentative and may get technical.

    So first, take a look at this link and realize that this is just a pool cleanup guy who doesn't know science [EDIT] (no offense intended and I'm sorry I didn't write that better -- the word "just" was particularly inappropriate and "maintenance" would be better than "cleanup" and "who isn't a scientist" would be better than "doesn't know science" -- I'm a skinny weakling who is also not a scientist if it helps balance that out) [END-EDIT] and he sometimes takes sources that have accurate information and misinterprets them. Nevertheless, there are a few points worthy of discussion:

    1) Does the splash-out (and dripping from bathing suits, etc.) of salt onto coping and other concrete and grout surfaces cause them to wear, pit or have other problems?

    2) Does the splash-out and dripping of salt onto metal surfaces (such as diving board mountings) cause them to rust more quickly?

    3) Do SWG pools increase corrosion rates of metal surfaces in the pool water such as copper heat exchangers? If so, why?

    [EDIT]
    4) Does the increased electrical conductivity from higher salt levels lead to greater shock risk with improper bonding?
    [END-EDIT]

    I'll just leave this as questions to mull over and think about for now. The responses may lead to ways of alleviating any of these issues, if these issues are real. I look forward to your comments and will add my own. No rush in this; I just wanted to put a placeholder here so we don't get too swayed by how perfect SWG pools are. Like most things in life, nothing is perfect and it's all about understanding the tradeoffs and compromises and making intelligent choices.

    [EDIT]
    Though this list can be debated, here's a starting point for discussion. I will expand and update this as we get more comments and information.

    PROS:
    • Less maintenance. Chlorine added automaticaly. No need to buy chlorine, physically carry it home, and add it regularly (possibly daily).
    • Lower possibility of developing algae, though this may be more related to the continual addition of concentrated chlorine rather than the SWG, per se.
    • Less burning or dry feeling in eyes. Salt in water is closer to salinity of human tears.
    • Water feels silkier.
    CONS:
    • Up-front cost is higher than other chlorine sources. On-going electricity cost may be lower. Salt cell replacement cost is high (every 3-5 years?).
    • pH often has a strong tendency to rise (so lots of acid needs to be added) unless partially mitigated by lower TA and use of Borates.
    • Increased corrosion rate of unsealed coping and hardscape surfaces through repeated splash-out and evaporation.
    • Increased corrosion rate of steel and cheap stainless steel surfaces that are not designed for salt water exposure, especially if no CYA is used.
    • Increased corrosion rate of copper heat exchangers and copper piping (if any) if no CYA is used and chlorine levels get high.
    • Splash out water may evaporate to leave more solid salt on surfaces than with non-salt pools.

    Look at this recent thread and now this thread for examples of corrosion posted to this forum. Also, this post describes corrosion of exterior lighting from the splashing of the pool cleaner.
    [END-EDIT]

    Richard


    This could be a good one so I stuck it to keep it at the top for now.
    Al
    Last edited by chem geek; 04-14-2007 at 12:59 PM. Reason: added "drying out" of eyes since "burning" is usually monochloramine, not lack of salt

  2. #2
    Davenj is offline Lifetime Member Thread Analyst Davenj 0
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    Default Re: Downsides to salt pools

    Had the pool vinyl IG for about 18 months, SWCG. Kool Deck, haven't noticed anything with that. The SS railing had a white gritty paste/slurry in the aluminum mounts in the deck. Noticed it when I removed them for the winter. Any suggestions for next season.

    Dave

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    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: Downsides to salt pools

    Dave,

    My guess is that the white paste is salt. If these mounts were in the deck, then splashed water could go into the mounts and evaporation would get rid of the water leaving the salts that are in the pool. Multiple cycles of water entry and evaporation would leave more and more salt. For an SWG pool, this would mostly be sodium chloride, but there would also be some calcium chloride as well (I assume that the bicarbonate would outgas with evaporation [EDIT] though you could have some solid sodium bicarbonate as well [END-EDIT]) and some sodium cyanurate. The next time this happens, or if the paste is still there, you can test it by putting a little in distilled water (or tap water, if you test the tap water separately) and then 1) see if the paste dissolves in water and 2) measure the salt (chloride) level. If it's high, then the paste is likely to be salt. You could also measure the CYA level to see if I'm right about the sodium cyanurate.

    As for what to do, there doesn't seem like much except putting some sort of waterproof caulking around the top of the mount against the stainless steel railing. You could probably very easily remove the caulking when you want to remove the railing at the end of the swim season. I'm not much of a mechnical guy so others would likely have better suggestions.

    Richard
    Last edited by chem geek; 01-02-2007 at 05:29 PM.

  4. #4
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    Default Re: Downsides to salt pools

    I've yet to have my system a full season so my 'down side' is limited. So far, its been all up side similar to:

    • Less maintenance. Chlorine added automaticaly. No need to buy chlorine, physically carry it home, and add it regularly (possibly daily).
    • Lower possibility of developing algae, though this may be more related to the continual addition of concentrated chlorine rather than the SWG, per se.
    • Less burning of eyes. Salt in water is closer to salinity of human tears.
    • Water feels silkier.


    My cons are limited as well:

    -The up front cost was well within my comfort zone.
    -I add a little more acid than I use to but thats a minor negative.
    -I have no metal ladders, rails or heat exchangers in my pool.
    -I hose off my pool deck and patio weekly during the swim season (did so before installing the SWCG) so I see no build up.


    basically, So far, so good.
    14'x31' kidney 21K gal IG plaster pool; SWCG (Saline Generating System's SGS Breeze); Pentair FNS Plus 48 DE DE filter; Whisperflow 1 HP pump; 8 hours hrs; kit purchased from Ben; utility water; summer: none; winter: none; PF:5.7

  5. #5
    Davenj is offline Lifetime Member Thread Analyst Davenj 0
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    Default Re: Downsides to salt pools

    Richard,
    I'll test the for salt in the paste next season. My CYA ran 50ppm. Good suggestion about the chaulk. I will try some DucSeal, it stays plyable and will be easy to remove.
    Thanks
    Dave

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    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: Downsides to salt pools

    Well so far, the two reports of corrosion in salt (SWG) pools on this forum have had possible alternative explanations other than the increased salinity. In this thread, it appears that the corrosion of stainless steel could be from the high effective chlorine levels due to not using CYA, though the very rapid speed of this corrosion may be due to multiple factors (including salinity) combined together. In this thread it appears that the quality of limestone is the critical factor and that salinity may play a far lesser role in this case.

    My gut feel on this is that different factors affect corrosion and can combine together as well. Therefore, blaming a single factor for corrosion is sometimes just used as an excuse. That does not mean that there are not situations where salinity causes greater corrosion, but that it may be getting blamed as the sole or primary factor in some situations where this may not be the case.

    Please continue to give us your stories and facts about corrosion you experience, as only a large number of cases will allow us to sort all of this out.

    Richard

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