Gravel, Sand, Charcoal: The Oldest Water Filter Still Works
Long before cartridges and replacement schedules, people cleaned water by pouring it through the ground — on purpose, in a barrel. A layered gravity filter is the same idea in a bucket: coarse gravel to catch debris, sand to strain the fine sediment, activated charcoal to pull out much of what you can taste and smell. You can build one in an afternoon from hardware-store parts.
The build in five lines
Food-grade bucket with a spigot near the bottom. A layer of rinsed gravel first, then activated charcoal (the aquarium kind works), then clean play sand on top, each separated by landscape cloth. Pour source water in at the top; let gravity do the work. First few batches run cloudy — that's the sand settling, keep going.
The honest limitation
A layered filter clarifies water — it does not sterilize it. Sediment, grit, and off-tastes are its job. Microbes are not. Water from an unknown source still needs a rolling boil (or proper purification) after filtering. Filter first, boil second: the filter keeps the sediment from scorching, and the boil handles what you can't see.
It's a good weekend build for the same reason it's survived a few thousand years: no moving parts, no cartridges to buy, and every part of it teaches you how water actually gets clean.
