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Thread: Evaporation

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    tcat's Avatar
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    May 2012
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    Evaporation

    I noticed last night I got more evaporation than I did during the day yesterday (no cover). Pool is shaded, but got about 25% of 80 degree sun. Was 50 last night, pool at 87 (now 82). Went down 1/16" yesterday, 1/8" last night. It's this normal? Does not go down with cover, so no leaks. Lots of steam at night, so I'm guessing the temp difference is causing the excess evaporation. Time to start using the cover again.

    IG pebble, 15,000 gallon
    48 PentAir DE Filter with backwash valve
    PentAir Whisperflo pump with 1hp 2-speed motor
    Aquabot 4WD, Poolskim
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    DIY chlorine feed
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    Richard320's Avatar
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    Re: Evaporation

    Wind seems to make more difference than temperature in my experience.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    JoyfulNoise's Avatar
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    Re: Evaporation

    It make sense you would lose it at night. Generally speaking the pool water temp will lag the air temp during the day and evaporation will be minimal. Once the air temp drops (and if the RH is low), the pool water will be much warmer than the air. Once the watt temp is even just a few degrees above the air temperature, evaporation rates will increase.

    It is better to keep the pool covered at night to reduce evaporative loss.
    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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    tcat's Avatar
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    Re: Evaporation

    Makes sense. Glad it wasn't windy! Funny, thought since day temps were above 80 I could start leaving cover off, but nights are still 40s and 50s. Losing an inch of water a week is 800-1000 gallons per month. Makes the labor of adding the cover easier!

    IG pebble, 15,000 gallon
    48 PentAir DE Filter with backwash valve
    PentAir Whisperflo pump with 1hp 2-speed motor
    Aquabot 4WD, Poolskim
    Intermatic Dual Timeclock with freezeguard
    DIY chlorine feed
    BBB

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    mas985's Avatar
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    Re: Evaporation

    The evaporation rate is dependent on the difference between the water temperature and the dew point temperature (air temp + humidity). So if the dew point temperature dropped at night, then evaporation would increase. However, air temperature can drop without the dew point temperature dropping and in that case, the evaporation rate would not change.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    DaninFLA's Avatar
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    Re: Evaporation

    humidity and wind are big components of evaporation. it can be hot and very humid and you can lose less water than on a dry/windy day
    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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    kywildcats's Avatar
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    Re: Evaporation

    Wind been blowing hard here all week, and I've noticed more water loss than usual.
    Mark
    20'x28' IG, Vinyl, (Sept 2015) 14,900 Gallon, 3'4 to 5'6 deep, SPLAPOOL 1.5 HP, 220v, 2 speed pump, Waterway Carefree 27" 400 LB Sand filter, Digital Nano plus SWG, TF-100 test kit /speed stir. Dolphin Primal x3 robotic cleaner

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