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I live in an all-electric home and when the power grid is out we have nothing. No water, no sewer, lights, cooking or anything else. I will have a generator to run sparingly to keep the freezer and the refrigerator going. Our home is a passive solar home with great insulation.

If the Cascadia Subduction Zone earthquake happens, the grid could be out for a year. During that time, with the well pump not working, we will need a source of clean fresh water.

A slow sand filter, made in a 55-gallon plastic drum, once set up and after running for a month or so, produces about 10 gallons per day of remarkably clean water.

The filter needs untreated raw water on a continuous basis. We intend to harvest rainwater from our shop roof to feed the biological layer of beneficial microbes that grow in the sand of the filter. We have two 1500 gallon tanks to store raw roof water to feed the filter on a continuous basis.

The filter is a gravity feed unit and I will feed it with raw water pumped with a small DC pump powered by solar PV panels and a battery.

I am just beginning the process of building one of these filters. I am currently working toward installing gutter screens. I have the two storage tanks and the drum to build the filter in.

If you have been thinking about this scenario, and would like to discuss this solution to the problem of having no fresh water for months and months, please join me at the Ferndale Library in the small conference room, on Tuesday December 13th from 7:00 PM until 8:30 PM. I hope to see you there.


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Comment by David Culver on November 23, 2016 at 12:58pm

The website where I have been learning about this filter is (

There is also a blog connected to that site with lots of information . 

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