Tap water is not safe to drink. Bottled mineral water is cheap and freely available. Use it for everything and if you are going anywhere remote take a good supply with you.
Should you find yourself desperate, thirsty and with nowhere to buy water, then try the following.
Boiling Vigorous boiling for one minute is the most effective means of water purification. At altitudes greater than 2000m (6500ft), boil for three minutes.
Purification pills Disinfect water with purification tablets, available at most pharmacies.
Filters Filters with smaller pores (reverse osmosis filters) provide the broadest protection, but they are relatively large and are readily plugged by debris. Those with larger pores (microstrainer filters) are ineffective against viruses, although they remove other organisms. Manufacturers’ instructions must be carefully followed.