In a SHTF moment, where your need for water is critical, purification of your water source is less of a priority than drinking it.

If you have the time, however, this is one primitive but effective method of purifying your water – that may not be as foolproof as purification tablets or a full boil, but would, if it was all you had, kill most parasites, bacteria and viruses in your water.

The key to this method is proportion – you must have enough rocks that are hot enough to bring your water to a boil.

If you achieve that, while this water purification method is not foolproof, if the alternatives are drinking non-purified water or not water at all, this method is effective.