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Thread: Evaporation question

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    Join Date
    May 2014
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    Waterloo, Ontario, Canada
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    Evaporation question

    I read somewhere that evaporation increases with water temperature. But what if the water is cold, but the air even colder. Last night we seem to have lost a quarter of an inch. The water temperature is 55 and the temperature got down to 36 overnight. Would you expect a lot of evaporation in those conditions? I tried the bucket test and I 'think' the bucket lost the same amount of water. I'm just questioning the validity of the test because the evaporation seems somewhat high to me.
    22k gal, IG Vinyl

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    Richard320's Avatar
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    Re: Evaporation question

    Evaporation increases more with wind than temperature. And low humidity also plays a factor. What's the weather been like, besides cold at night?
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    Re: Evaporation question

    Hi Richard,

    Thanks for the reply. According to this site Yesterday's and last weeks' weather in Waterloo, Ontario, Canada, the wind was fairly low, averaging around 10 km/h (6 mph) and the humidity was around 50%.
    22k gal, IG Vinyl

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    triptyx's Avatar
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    Re: Evaporation question

    A 20 degree difference between the water and the air, and considering cold air can hold less moisture than warmer air, could cause evaporation. I would think that the key will be to see if it continues to lose that much water regularly - then you can start worrying about a leak.
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    mas985's Avatar
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    Re: Evaporation question

    It is the difference between the water and air vapor pressures that drives evaporation. So if humidity is lower than 100%, the water and air temperatures can be exactly the same and evaporation still occurs.

    For those temperatures ranges and humidity, 1/4" is a bit high but if you don't have much of a wind break (e.g. trees, buildings, etc) around the pool, it is possible.
    Mark
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    Waterloo, Ontario, Canada
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    Re: Evaporation question

    Thanks for the responses. I guess I'll just keep an eye on it and retry the bucket test tonight.
    22k gal, IG Vinyl

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