I don´t understand why people feel the need to buy bottled water if they live in a country where the tap water tastes ok and is safe to drink. For example, when I go walking in Spain I never buy water as what comes out of the tap is fine and all towns and villages have public water fountains where you can fill up as you walk through. If the water is not drinkable there is a notice which says so.
Unfortunately here the tap water has an unpleasant mouldy taste and I´d rather not drink it. I buy my water in a 20 litre bottle which is reusable. The chap who delivers it takes the empty one away for re-filling. Our tap water is fine for showers, washing and dishes, etc, and I´ll use it for cooking things which are going to be strained but for tea, soups and stews I´ll use the bottled water because of the taste.
A bottle like this lasts me about ten days and costs around three pounds which I think is good value for money.