Nadi Filter (Clay Pot Filter)

A nadi is basically a clay pot that has been used for storage in many countries for centuries and is the main component of the filter.  You start with a 30-35” tall nadi and make a hole in the side of it about 20” off of the ground.  You then put a piece of flexible pipe through the whole in the side with one end reaching the bottom of the nadi and the other end protruding out of the side, and then seal around the whole in the side of the nadi.  From here you basically are adding stones and sand.  Layer 1 (bottom layer) is one layer of “potato sized” rocks.  The gaps between these larger rocks will let water flow between them and into the pipe.  From here you add successive layers of smaller rocks.  For the second layer you use smaller stones that will help fill the gaps between the potato rocks, but will also keep the smaller rocks in layer three from slipping through.  Layer 3 is smaller gravel rocks, followed on layer 4 with seed sized rocks.  On top of layer 4 you then place sand until you’re about five inches below where the pipe exits the filter.  At this point you get a mutca, which is a best described as another clay pot that goes on top of the nadi, and put a nail sized hole it.  This is what you pour the water into, and the nail sized hole lets it slowly drain into the nadi.  The last step is to put a cloth over the top of the nadi, place the mutca on top of it, and then tie the mutca to the nadi.  That’s it!  It’s so simple and once you have the materials it can be put together quickly and you can be drinking clean water in no time. So how does rock and sand filter the water?  It’s all about biology.  There are “good” microbes and “bad” microbes.  The bad microbes are what cause disease and bacteria.  This filter works by giving the good microbes a place where they can set up a home and reproduce; the sand.  Because the sand has so much surface area in all the little pieces it gives a lot of room for the good microbes to hold onto and grow.  As time goes on the microbes continue to multiply on the sand.  After about 3 weeks there are enough good microbes eating the bad microbes for the water to be considered very clean and good to drink.  Then all you have to do is add dirty water to give the good microbes a supply of food (the bad microbes), and what comes out is clean water.