Waterdrop gravity-fed water filter system with stainless steel tank ... that can be useful for capturing attention during an emergency. Get a two-pack from Amazon for $19.99.

LifeStraw’s Peak Series of water ... and gravity-fed filter systems. Even if you don’t expect to need it, having a LifeStraw offers peace of mind and can be a lifesaver in an emergency.

A sand filter, or "filtration basin", is a stormwater quality treatment system that works by ... At first, the water pools on top of the filter material, held in place by the banks. Gradually, gravity ...