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.