Open-Source Ceramic Water Filters: DIY Purification That Scaled to 39 Countries

The ceramic pot filter is a decades-old, deliberately low-tech answer to unsafe drinking water, and this Low-Tech Lab tutorial walks through how it works and how to manufacture it at semi-industrial scale. The core mechanism is simple physics: clay is mixed with a combustible filler like sawdust or ground rice husks, then fired in a kiln. The filler burns away, leaving a network of cavities and pores measured between roughly 0.6 and 3.0 microns — small enough to mechanically trap and adsorb bacteria, protozoa, helminths, and sediment as water seeps slowly through the pot into a storage container below. A coating of colloidal silver adds an antibacterial layer that inactivates pathogens and keeps the filter itself from becoming a growth medium. Getting the clay-to-filler ratio and pore size right is the whole game, which is why the guide stresses material testing and warns this is an entrepreneur-scale build, not a kitchen-table project.