Mass Evaporation

I’m sure this isn’t correct as I think we must have big problems with the pool = like a hole in it. If we fill it up during the day, overnight the level goes down by a good foot or so . The landlord seems to think that that is evaportaion - but working it out that mean we loose 21,600 litres a night - which can’t be right. (Just to make you jealous the pool is a delicious 20′ x 40′ and will be lovely when its not leaking.)