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Thread: Effects of Rain

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    TrevNJPool's Avatar
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    Effects of Rain

    What effects does a large amount of rain have on pool chemistry besides the obvious dilution of FC and minutely lowering CYA.
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    jrs_diesel's Avatar
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    Re: Effects of Rain

    The aeration from all of the raindrops will raise PH, mostly dependent on how much and how hard the rain falls.

    It will also dilute the CH level as well.
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    Mod Squad pooldv's Avatar
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    Re: Effects of Rain

    Biggest impact for me has been dilution of CYA and salt. Had to add quite a bit more this spring than ever before. PH and chlorine levels normally need to be tweaked this time of year anyway as the water warms and the sun comes out more. I haven't really noticed much PH/FC issues related to rain.
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    Re: Effects of Rain

    Rain has no effect on FC and no effect on CYA and Salt. pretty much no effect on anything, UNLESS, you are getting so much rain that water is overflowing from the pool. you are going to have to refill the pool to account for evaporation anyway, so rain just does it for you. not sure where the thought that rain affects chlorine came from....probably from the pool store, lol. I agree that pH could be affected by the rain, but not sure how much.

    For example, say your pool has an average depth of 5 feet. if you get a large rain event, say 2 inches total. that's only a 3.3% increase in pool volume. so if you had a FC of 6.0 before the rain, now it would be 5.80, but that difference is not detectable in testing (0.5ppm per drop). Same with CYA. if you had a CYA reading of 50, after the large rain it would be 48.35. once gain, that small of a change is not detectable via testing.

    You also have to consider that the extra water will evaporate and your pool will be back to the original level eventually. its no different than filling up your pool with the hose to top off due to evaporation loss. if you are somewhere that's getting a ton of rain and your pool is constantly overflowing then it can make a small difference.

    The only affect rain would have on water chemistry that I can see is if the rain results in blowing a lot of stuff/organics into the pool, which would eat up FC.

    Long story short, don't worry about the rain
    Dan
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    Mod Squad pooldv's Avatar
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    Re: Effects of Rain

    That is generally true except that it is raining so much that my overflow pipe pretty much has not stopped overflowing and taking my cya and salt with it.
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    Re: Effects of Rain

    Quote Originally Posted by pooldv View Post
    That is generally true except that it is raining so much that my overflow pipe pretty much has not stopped overflowing and taking my cya and salt with it.
    yes, like I said. if water is overflowing from the pool then that's different. most rain events are contained in the pool, but for some reason there is a misconception that rain eats up chlorine. I even saw it on a pool store website. it said that biggest contributor to chlorine loss was rain. I almost spit my coffee on my keyboard.

    and things are a bit different in Texas right now, lol.
    Dan
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    TrevNJPool's Avatar
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    Re: Effects of Rain

    I just figured it was un treated water mixing with the pool water so dilution would occur. Didn't think it would be a big difference. Thanks for the input.
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    Mod Squad pooldv's Avatar
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    Re: Effects of Rain

    Quote Originally Posted by DaninFLA View Post
    yes, like I said. if water is overflowing from the pool then that's different. most rain events are contained in the pool, but for some reason there is a misconception that rain eats up chlorine. I even saw it on a pool store website. it said that biggest contributor to chlorine loss was rain. I almost spit my coffee on my keyboard.

    and things are a bit different in Texas right now, lol.
    Yeah for sure! We just broke the intergalactic rain record for May in the history of all mankind!
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    Re: Effects of Rain

    Hasn't there been more than 7" of rain in the past week or so? (Probably more, haven't been able to watch the news much) that is significant.
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    Mod Squad pooldv's Avatar
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    Re: Effects of Rain

    There was 7" one day and a couple more the next. Our lake went from 13' low and not full since 2011 to 14' above full pool with all gates open. Totes craziness.
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    Re: Effects of Rain

    We had a "supercell" few yrs back. After the I first scary as **** down pour ended n our property survived the creek n from the hills run off. I pulled a Lt Dan like in forest Gump. Boy what a mistake, we then got 8" in only 3 hours. Had to build a dam around back of house n move my cars so they didn't get washed away! Lmao never again will I play the Lt Dan card! Pool was fine though
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    Re: Effects of Rain

    We had a lot of rain here in Houston as well. Craziness with all of the rain, and I'm glad we finally have a dry week. Our pool topped out twice this year so far and came real close to doing it a third time two weeks ago. Two of those events, it topped out before it stopped raining so I lost CH and CYA due to that, on top of the losses from me pumping out the extra water and bringing the pool back to normal level.
    J.R.

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    Re: Effects of Rain

    Quote Originally Posted by pooldv
    We just broke the intergalactic rain record for May in the history of all mankind!
    I'll second that. Measurable rain at DFW 24 out of the 31 days of May and most of these were heavy rains.

    Although my CYA levels were substantially lowered when all that rain forced significant amounts of water to drain through the overflow pipe and into the alley, it did lower my CH levels along with it.
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