Ideally, you should change your water bottles every time you change your watch. If necessary, you can use water from the toilet cistern or water heater. The short answer is that you need at least 14 gallons of water per person. That breaks down to 1 gallon per day for 2 weeks.
Rod Brouhard is a Paramedic Emergency Medical Technician (EMT-P), journalist, educator and advocate for emergency medical providers and patients. The 72-hour kit contains supplies to help you and your family for three days in an emergency situation. After starting to store food, many people find that it actually frees up a good chunk of their regular weekly food budget, even without using coupons. A zip lock dry food bag in an inexpensive food storage container works well for storage and discourages rodents from getting to the food.
If you wear glasses or contact lenses, be sure to carry the extras in your emergency kit, along with the supplies you need with them (contact solution, eyeglass repair kit, etc.). It is advisable to have a supply of disposable dishes and utensils to use in an emergency if there is no water available. Hand sanitizer should also be included in your emergency supplies to prevent the spread of illness after a disaster.