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Thread: Evaporation

  1. Back To Top    #1

    Join Date
    Mar 2009
    eastern washington state


    I have new/last year 18x36 vinyl pool. Its seems like i am loosing allot of water.. Was just wondering what a normal evaporation rate would be.. with no one in the pool about how much would a person loose.. I am thinking that i have a leak somewhere. I cant see where it is leaking and no bubbles in the liner...i have not done the bucket test. but was just wondering what a normal evaporation rate would be... i live in eastern wash temp is around 90 and very dry..
    live in eastern washington state
    18x36, Vinyl inground 24k
    Hayward 1 hp filter pump
    1 skimmer/2 returns
    24" sand filter, polaris 280 with booster pump.

  2. Back To Top    #2
    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: Evaporation

    Average loss over a year is in the range of 50-60" for your area but summer time is usually twice the average rate so it could be as high 2" per week and maybe even 3". If in doubt, do a bucket test to see if the pool loses water faster than a bucket on the first step at the same starting level.
    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

  3. Back To Top    #3
    stev32k's Avatar
    Join Date
    Mar 2009
    Mobile, Alabama

    Re: Evaporation

    I believe I would call your local county extension agent. He can probably give you the local evaporation rates off the top of his head. Those guys keep up with that sort of thing. He will give you a number in inches per year or maybe inches per month. You can then measure the water drop in your pool to see if it is in that range.

    Eastern Washington is pretty dry and about like western Oklahoma where I grew up. Out there the annual evaporation rate was 66 inches, the annual rain fall was 9 inches so one could expect .15 inches per day water drop on average.

    A mas985 says the easiest way is just put some water in a bucket - measure the loss every day and compare it to your pool loss.

    P.S. Make sure the bucket sides don't get direct sunlight. You could put it in the pool so the water temperatures would be the same.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

  4. Back To Top    #4

    Join Date
    Jun 2008
    Buffalo, NY

    Re: Evaporation

    Not to hijack, but i was worried too, about a leak. Its my second summer owning this pool and I didn't know that you could have "inches per week" of evaporation. Its been a couple of months now and I am filling my pool a bit for the first time. I thought the rain would help keep it filled, but I guess not. lol
    18ft Round x 4ft deep AGP. Approx 7800 gallon.

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