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Thread: Pool Evaporation

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    Pool Evaporation

    How much is a realistic amount of water to lose due to evaporation? Just wondering if we have a small leak or just losing water due to evaporation. Losing about an inch a week.
    16'x34' Inground Vinyl Pool. 65,500L. Hayward S244T2 24 Sand Filter. Hayward 1hp Super Pump. Raypak PR266 EN 266,000 btu,. AquaRite SWCG. Aqualamp LED 2 w/ remote

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    Texas Splash's Avatar
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    Re: Pool Evaporation

    An inch a week may not be too extreme depending upon the amount of sun/heat you receive. Here are a couple pages that I hope will help you:
    Water loss...how much is normal?????
    Pool School - Leak Detection
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Divin Dave's Avatar
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    Re: Pool Evaporation

    you can always do a bucket test to confirm it.
    Tips - Bucket Test - Test your pool for leaks
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
    www.tftestkits.net Experience- it's what's learned just after you needed it most !!

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    Mod Squad woodyp's Avatar
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    Re: Pool Evaporation

    I'd be ecstaticwith 1" per week...........(in Texas).
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
    2 Speed Hayward Power-Flo Matrix 85 g.p.m. 22" 250lb. sand filter hard plumbed
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    DaninFLA's Avatar
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    Re: Pool Evaporation

    I am in Florida, so a bit hotter and I lose probably around 1/4" a day during very hot and windy days. the wind is a big factor in evaporation.
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    Re: Pool Evaporation

    As was noted, wind is a huge factor. Relative humidity is another factor where you won't get evaporation when it's near 100% while in dry low humidity climates such as desert areas you get more evaporation. Water temperature is also a factor. The following shows how these factors come into play starting with a baseline of 85F water temperature, 80F air temperature, 50% relative humidity, and no wind at the pool's surface.

    Variation of evaporation with wind
    0 MPH .... 0.21"/day
    1 MPH .... 0.31"/day
    2 MPH .... 0.40"/day
    3 MPH .... 0.50"/day
    5 MPH .... 0.69"/day
    7 MPH .... 0.88"/day
    10 MPH .... 1.17"/day

    Variation of evaporation with water temperture
    70F .... 0.07"/day
    75F .... 0.11"/day
    80F .... 0.16"/day
    85F .... 0.21"/day
    90F .... 0.28"/day
    95F .... 0.35"/day
    100F .... 0.44"/day
    105F .... 0.54"/day

    Variation of evaporation with relative humidity
    0% .... 0.37"/day
    25% .... 0.29"/day
    50% .... 0.21"/day
    75% .... 0.14"/day
    90% .... 0.09"/day
    100% .... 0.06"/day (evaporation still occurs in this case because air is cooler than water so is less than warm water vapor saturation; if the same temp then no evaporation)

    Variation of evaporation with air temperature
    60F .... 0.29"/day
    70F .... 0.26"/day
    80F .... 0.21"/day
    90F .... 0.15"/day
    100F .... 0.08"/day

    Based on this link for Toronto, I'll assume during the day 80F air temperature with 55% relative humidity and nighttime 65F air temperature with 90% relative humidity. If you are gas heating the pool to 80F, then with no wind the evaporation would be 0.14"/day during the day (0.98"/week) and 0.15"/day at night (this is typical where day and night evaporation is the same unless humidity gets to 100% at night and water comes out of the air as dew). With 1 MPH wind, it's 0.21"/day, with 2 MPH wind it's 0.27"/day, with 3 MPH wind it's 0.33"/day, with 5 MPH wind it's 0.46"/day. However, if you are using a pool cover, then there should be no evaporation.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Pool Evaporation

    Wow!! Thanks for all the info! Will read up and try the bucket test.

    If using a solar cover, should I leave it off for 24 hours to test with the bucket or how do I do it?
    16'x34' Inground Vinyl Pool. 65,500L. Hayward S244T2 24 Sand Filter. Hayward 1hp Super Pump. Raypak PR266 EN 266,000 btu,. AquaRite SWCG. Aqualamp LED 2 w/ remote

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    JoyfulNoise's Avatar
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    Re: Pool Evaporation

    Is there a good calculator for evaporation rate as a function of the various parameters mentioned?

    I was in another thread where the OP was asking about salinity increase due to evaporation and high salinity fill water. It would be nice to be able to point folks towards a calculator if one is available.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Divin Dave's Avatar
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    Re: Pool Evaporation

    I would leave the pool and bucket uncovered for the day, so that temp, wind, humidity, etc is all constant.

    Quote Originally Posted by Shaf77 View Post
    Wow!! Thanks for all the info! Will read up and try the bucket test.

    If using a solar cover, should I leave it off for 24 hours to test with the bucket or how do I do it?
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
    www.tftestkits.net Experience- it's what's learned just after you needed it most !!

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    DaninFLA's Avatar
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    Re: Pool Evaporation

    Quote Originally Posted by JoyfulNoise View Post
    Is there a good calculator for evaporation rate as a function of the various parameters mentioned?

    I was in another thread where the OP was asking about salinity increase due to evaporation and high salinity fill water. It would be nice to be able to point folks towards a calculator if one is available.


    Sent from my iPhone using Tapatalk
    not sure why that would really be helpful? the main issues with evaporation, especially fast evaporation is people being concerned about having a leak. that is easily confirmed with the bucket test. as far as a calculator, not sure how helpful that would be, being that humidity, air temperature and wind speeds are so variably over a 24 hour day. you just wouldn't get great results. if your bucket tests confirms 1/4" per day, etc, that what it is. it really doesn't matter if you use a calculator and determine you "should" be getting 1" of evaporation and really get 1.5". if there is no leak, then you are losing 1.5" to evaporation no biggie.


    as far as figuring out salinity increases, that's pretty simply. if you have an average depth of 4 feet in your pool, and you lose 1" that's 2% of volume decrease. so everything increases by 2%. 3500ppm salt becomes 3570ppm. negligible, and not within the range of testing. its the same issue with rain , the increases in total volume of the pool is so small its negligible

    as far as someone filling up the pool with high salinity water, not sure on that thread, but that can be calculated pretty easily too. all you need to know is how much each inch of pool water is on a percent of the pool volume. if you know the salinity of the water being added, you can calculate the total increase in ppm per inch of water refilled. evaporation really isn't a factor in determining that, just the total volume added each time and keeping a running tally of salt ppm. but again, I don't think that is a very common practice at all.
    Dan
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
    Pool School - Chlorine / CYA Chart; Pool School - Test Kits Compared;

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    JoyfulNoise's Avatar
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    Re: Pool Evaporation

    Quote Originally Posted by DaninFLA View Post
    not sure why that would really be helpful? the main issues with evaporation, especially fast evaporation is people being concerned about having a leak. that is easily confirmed with the bucket test. as far as a calculator, not sure how helpful that would be, being that humidity, air temperature and wind speeds are so variably over a 24 hour day. you just wouldn't get great results. if your bucket tests confirms 1/4" per day, etc, that what it is. it really doesn't matter if you use a calculator and determine you "should" be getting 1" of evaporation and really get 1.5". if there is no leak, then you are losing 1.5" to evaporation no biggie.


    as far as figuring out salinity increases, that's pretty simply. if you have an average depth of 4 feet in your pool, and you lose 1" that's 2% of volume decrease. so everything increases by 2%. 3500ppm salt becomes 3570ppm. negligible, and not within the range of testing. its the same issue with rain , the increases in total volume of the pool is so small its negligible

    as far as someone filling up the pool with high salinity water, not sure on that thread, but that can be calculated pretty easily too. all you need to know is how much each inch of pool water is on a percent of the pool volume. if you know the salinity of the water being added, you can calculate the total increase in ppm per inch of water refilled. evaporation really isn't a factor in determining that, just the total volume added each time and keeping a running tally of salt ppm. but again, I don't think that is a very common practice at all.
    Thanks for the post. I agree that there are certainly rough, ball park figures you can calculate but my original question had a different intent. Perhaps I will ask it over in "The Deep End" forum as opposed to cluttering up this thread.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Pool Evaporation

    For what it's worth, I'm in Burlington and use a solar cover whenever we aren't swimming.. Rain typically more than makes up for evaporation in my pool an I end up having to drain off some water at least twice a summer.
    16' wide ~20,000gal IG vinyl lazy L shape pool circa 2002, 1hp Hayward Super Pump, Hayward S244T sand filter, Hayward H250ED2 gas heater, Hayward eVac Pro robot, Stenner pump for chlorine, TF-100 test kit
    2008 Gulf Coast 864 LEi hot tub

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