We have a borehole on our smallholding with a 5000 l deposit which decants into a 300 l tank for domestic use. Sometimes, for one reason or another I have to fill this 300 l tank by operating a tap - as opposed to it filling up automatically - and so know from experience how far a 300 l tank goes. Our water is pumped out of the 300 l tank by an electric motor whenever a tap is turned on, so all the taps are "power shower".
A long shower, such as taken by visiting teenage kids flattens the 300 l in 10-15 mins. A normal shower uses 100 l. My wife and I can just about get by on 300 l a day, but barely. In normal use we would use 600 l day for the 2 of us, including 1 or 2 showers each daily , washing machine 3 times a week, dishwasher daily. This does not include watering of garden, flower pots, etc which takes another 300 l in 10-15 mins (twice a day in summer)
So, if there's more than 2 of you, particularly incl kids, I wouldn't be surprised if you used M3 a day. I don't know how much a pool uses, but could imagine top-ups could use 300 l a pop in summer.