Of course, some may argue there's a difference in taste - and that's really down to personal choice. But when it comes to cost, tap water compared to bottled water does really rather well... 100 litres of tap water costs less than one litre of bottled water. When we crunched the numbers, we found pouring 100 litres of tap water in Manchester in one day would cost you just under 18p for the lot, yet if you bought the same amount of Evian it'd be just over £40. Tap water is more environmentally friendly. The House of Commons Environmental Audit Committee found that sending plastic bottles to landfill or incinerating them produces approximately 233,000 tonnes of CO2e emissions a year.
Tap water meets health regulations.  Bottled water's often cited as being purer. However, the principal inspector from the Drinking Water Inspectorate told us:
Both tap water and bottled water are required to meet specific regulations which are in place to ensure both are safe to drink.