You will find in our apartments and at the beach studio reusable bottles to put water and take it with you. The tap water is drinkable and as you can see at the foto above, you can even refill your water bottle below the main square of the village.
Remember that you are on an island with limited resources, so please do not waste water. Stop the tap while brushing your teeth, soaping your hands, shaving. Try to have short showers and please use the tap in the village only to fill your water bottle. Do not clean there your stuff. There is a tap at the end of the main beach to clean your stuff, cause the sand could cause blockage to the sewage system (we do not have the best one and that is why you can also not throw paper in the toilet.).
Below we show you in google maps, where you can clean your beach stuff from the sand (where the red x is).
Yannis and Stella @Apollon, Naxos 