This group stresses being able to stay alive for indefinite periods in life-threatening wilderness scenarios, including plane crashes, shipwrecks, and being lost in the woods. Concerns are: thirst, hunger, climate, terrain, health, stress, and fear. The rule of 3 is often emphasized as common practice for wilderness survival. The rule states that a human can survive: 3 minutes without air, 3 hours without shelter, 3 days without water, 3 weeks without food. 
Again, the reason we tend to look sideways at those who get a little too into prepping for an apocalypse is because of their smug optimism. People actually being realistic about a dangerous future would be better served joining the military or ingratiating themselves with high-level government officials than agonizing about a little mouth scuzz or foot fuzz, right?
When a disaster strikes, there is no time to gather items before rushing out the door. Protect yourself and your loved one by keeping the SDS 3 Day Survival Backpack for 2 People in a convenient place so you are prepared for anything. This emergency prepping bag keeps you ready for even the worst situations. The American Red Cross recommends food, water, and emergency blankets to be included in such kits, but we have provided you with additional survival items for your safety and comfort such as ponchos, dust masks, first aid kit, radio, flashlight, charger, hand warmers, emergency whistle/compass, multiuse pocket knife. The 40-liter bag comes prepacked and is approximately 14” x 9” x 22” inches with additional packing room. Water-resistant, not waterproof. WARNING: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
Thomas spoke about these in his article on purifying contaminated water. Basically, the reverse osmosis water purification systems, like the one featured as #5, will take care of larger contaminents. Couple that with ultraviolet disinfection and the rest of water purification is pretty well taken care of without requiring anything too expensive. Remember that this system requires electrical power, so you’re going to need to take that into consideration. But with a solar panel generator, it’ll do the trick perfectly.