Are Gravity-Bag Filters Good for Urban Survival Kits?

Understanding the Filter

A gravity-fed filter, such as the Sawyer Mini or the MSR TrailShot, can be an effective addition to an urban survival kit. These filters use a simple, one-way flow of water through a membrane or filter element to remove contaminants. They are generally inexpensive, lightweight, and easy to use.

Filtering Water in Urban Environments

When selecting a gravity-fed filter for an urban survival kit, consider the types of contaminants you are likely to encounter. In urban environments, water sources may be more likely to be contaminated with bacteria, viruses, and particulate matter. A filter with a porosity of 0.2 microns or less can effectively remove these contaminants, making it suitable for urban survival kits. For example, the Sawyer Mini filter has a porosity of 0.1 microns and can remove 99.99% of bacteria, including E. coli, and 99.9% of viruses, including norovirus.

Maintenance and Use

To ensure optimal performance, gravity-fed filters should be regularly cleaned and maintained. This includes backflushing the filter to remove debris and particulate matter that can clog the filter element. It’s also essential to follow the manufacturer’s guidelines for filter replacement and maintenance to ensure the filter remains effective. For example, the Sawyer Mini filter can be backflushed using a syringe to remove debris and maintain its effectiveness. By following proper maintenance and use procedures, gravity-fed filters can provide reliable access to clean drinking water in urban survival situations.