A good, high quality filter is indispensible. Sawyers products are top notch. As already stated, 2 is 1, 1 is none. I prefer more than 2 options. The best I've come across for the highest filtration ability is the HydroPack. It will work even if you threw it in a well used Portapotty. Its slow, and single use, but it is highly effective and adds electrolytes.