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Thread: Normal Evaporation?

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    Question Normal Evaporation?

    I have been monitoring the water level in my in-ground spa daily for the past 25 days with the auto fill off & the auto cover on (except as noted below). The reason? To rule out a possible leak. The results thus far are as follows:

    Day 1 - 20: water level: -5/8" (air temperature = 85 - 90F).
    Day 21 - 22: water level: -11/16" (cover off for 32 hours while SLAMming; air temperature = 93 - 97F.
    Day 22 - 25: water level: -1/8" (air temperature = 96 - 99F).

    Please note that the spa was used approximately every other day by my wife & I for about 1/2 hour during the 25-day period. There was no measurable splash-out ( even into the auto cover vault). The spa holds 2,500 gallons & has a surface area of 10' X 14".

    My question: Is it reasonable to assume that the decreases in water level noted above can be attributed solely to evaporation? Thank you kindly.
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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    Re: Normal Evaporation?

    Seems reasonable. We have higher temps here (105-110 this time of year) and we probably lose a bit more than that with the cover on.
    50,000 gallon plaster in-ground salt pool with two 60 sq ft DE filters, two Intellichlor IC60 SWGs, two Intelliflo VS pumps, two Whisperflo pumps, two Pentair 400K BTU NG heaters, PCC2000 in-floor cleaning system...two everything.

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    Mod Squad pooldv's Avatar
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    Re: Normal Evaporation?

    Yes, 1/8-1/4 per day is normal evaporation without a cover. It could be about half that with a cover.
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    mas985's Avatar
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    Re: Normal Evaporation?

    With a cover that covers 100% of the water surface, evaporation should be almost non-existent. Although I might classify 5/8" over 20 days as almost non-existent.
    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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    Re: Normal Evaporation?

    Thank you for the feedback. The thought also occurred to me that whenever the cover is retracted some water will be pulled into the cover vault. And speaking of incidental "spashout", is the amount of water that will cling to a person (assumingly wearing swimsuits) be of any significance as far as lowering the water level? (I have to admit that it seems like a silly question, but I have been surprised by the answer to stupider questions before). Nevertheless, I had to ask.

    Thanks.
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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    Re: Normal Evaporation?

    First the best method to test for a leak vs evaporation is the bucket test. Place a bucket in a shallow area of your pool and fill it so the pool and bucket water levels are equal. If at the end of a few days they have different levels you most likely have a leak. I think you have evaporation but I would do the bucket test.

    Even in a 2500 pool the amount of water on your clothing is negligible. usually less than a cup.
    22k gallon IG pebblefina, Jandy 1.5 HP VS, Jandy CV Cartridge filter, Fafco solar panels, Polaris 360 supply side cleaner, waterfall

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    Re: Normal Evaporation?

    Bucket test! Brilliant! So simple & so obvious. The bucket is in the spa & I will report back in a few days. Thank you!!
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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    Re: Normal Evaporation?

    Well, as promised, here are the results of the "bucket" test over the past 6 days. With the spa covered (except for about 1/2 hour of daily usage in the late evening), the water level in the spa fell 3/16". Air temperature: 87 - 100℉. Interestingly, the water level in the bucket fell 7/8" during the same period. I suspect that since the bucket was placed under a 1" opening in the auto cover, that might account for additional evaporation.

    So, from your responses earlier, I assume that the decrease in the spa's water level was more than likely due to evaporation rather than a leak. Sound right?

    Thank you for your help.
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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