Thanks I haven't done the actually bucket test to figure out the evap rate. But I have used formulation tables to figure out the possible rates using humidity, wind speed, water temp, and air temp. And I have roughly figured that it would take 15 gpm being pumped in to keep up with 0.3 inches a day loss by evap. But as I said the evap rate changed by the day. So I am just at a loss to get exact calculations and to see if he has a possible leak as I can't find an obvious one anywhere.
