Had 4 of us in the tub on Saturday night for a fair few hours, and thought nothing of it when I had to top up at least 30-40mm on Sunday morning.
Then with only light use for a few days, I noticed again on Wednesday that I needed to top up the same again.
At this point, i was concerned that i might have a leak, so I topped it up to a distinctive line on the skimmer, so that I could monitor it.
I've left the covers on for over 36 hours, and taken another look this morning, to find that it's only dropped by about 1mm.
So I'm now satisfied that the losses earlier are more than likely down to spillage, absorption and evaporation.
So what sort of losses does everyone else experience?