We’re excited about two developments regarding Biosand Water Filters!
First, we have a Metal Fabrication class which is building a metal form, for pouring the filter vessels! This form will be invaluable when we get to Tanzania. We will use it first to make filters, and then–more importantly, we will show it to our local “metal fundi” so he can build more, just like it! It really helps to see what the finished product looks like, and how it works. Here’s what one of these forms looks like.
We also have just found a set of plans for making one of these forms out of plywood! We found this online, at ohorizons.org. I’m fairly handy with wood, so by next week, we hope to have one of these built. We suspect these may not last as long as the metal forms, but the cost is much lower and the technology is much easier. 
Either of these forms makes a concrete vessel for a water filter that will produce as much as 36 gallons of clean water per day! The science behind these filters is very interesting. In nature, water is purified by flowing through sand and gravel and by exposure to the sun. This system, developed by a scientist at the University of Calgary, removes up to 99% of all pathogens from dirty water!
ralphwwilliams 