I am going on a backpacking/hiking trip and will be outdoors for about four days, would you recommend a water filter.

You can try the Sawyer Squeeze Water Filter System. It’s a 1 x 16 ounce soft bottle with a plastic syringe for cleaning, hydration system adapter, and a straw. You can drink directly from the Sawyer Squeeze but most people squeeze untreated water through it from a soft bottle to a clean container. The filter uses a hollow-fiber membrane filter that removes 99.99999% of all bacteria, such as salmonella, cholera and E.coli and removes 99.9999% of all protozoa, such as giardia and Cryptosporidium. The filter itself weighs 3 ounces. https://iwaterpurification.com/best-filtered-water-bottle/