In case of an emergency, can I drink the water from my rain barrel? - You can NOT drink the water directly from the rain barrel. You need to filter the the water first with a emergency purification filter/product that is designed to take out contaminants, bacteria, viruses, etc.
Are ALL emergency purification filters the same? - No, there are differences between purification filters. One style is a ceramic filter style where the water was pushed through. The ceramic filter technology was based on microns and is an older technology. Now most filters today are based on hollow fiber technology. This new technology usually offers added viral and bacteria protection without the need for chemicals. There are many good emergency purification filters on the market today. You need to do your own research when choosing and decide what is best for your needs.