If the water from your tap is clear then purify by:
Boil it for three minutes. This kills disease-causing bacteria and parasites, OR
Add 1/8 teaspoon household bleach per gallon of water. Let it sit for 1/2 hour.
If water is cloudy:
Pour it through a coffee filter and boil it for three minutes. If you can't boil it, filter it and add 1/4 teaspoon of bleach per gallon. Let it sit for one hour.