Potable water from a DIY slow sand filter?

We have had a number of questions, over the past 5 years, about drinking the water from the slow sand filters described on this blog and on the websites associated with this blog. I’ve responded periodically to each comment, but still get people asking questions like the most recent one: “have you drunk this water yet and did you get sick?” I’ll attempt to respond to that issue, again, here. We do not drink the water from the filters on a regular basis. However. . . given an emergency situation. . . .  make your own choices and be responsible for them.   And, know that with knowledgeable maintenance, these filters are capable of producing high quality water; far superior to water in a mud puddle, or contaminated water from a damaged public water supply; and furthermore, slow sand water filters are used throughout the world to produce clean water.

The filters we have built and tested here produce water that meets and/or greatly exceeds EPA standards, and local county standards for drinking water. The outputs have been tested repeatedly by EPA certified laboratories:

The City of Everett, Washington Environmental Laboratory
AmTest in Kirkland Washington

The filters have been shown to provide water that exceeds the EPA standards for:

  1. Coliform bacteria
  2. Arsenic
  3. Zinc
  4. Nitrites
  5. Nitrates
  6. Sodium
  7. Silver
  8. Barium
  9. Cadmium
  10. Selenium
  11. Chromium
  12. Mercury
  13. Lead
  14. Fluoride
  15. Total Petroleum Hydrocarbons sometimes called TPH
  16. Total Organic Carbon sometimes called TOC
  17. E Coli bacteria
  18. Fecal Coliform bacteria
filter_tests

this test is of the output water

EPA contaminant level limits

Know that the fact that the filters pass these tests is only valid for these filters here, and this water here. There are limits to what these filters can remove from water. Super high concentrations of bacteria, or chemicals cannot be adequately removed without proper testing and design.

Most importantly: we cannot, I repeat, cannot guarantee the water quality from any of the filters we describe here and/or on the websites (listed below). Anything can be in water – ANYTHING. Every situation is different. Do not drink water from any source without first having it tested by a knowledgeable person. If you choose to drink the water from one of the filters we describe – that you build, or that we build – you do so AT YOUR OWN RISK. These filters, just like a private water well, must be monitored and maintained constantly. Any private well is subject to contamination at any time. So are these filters. Public water systems are monitored by professionals who know how to test water, and are responsible for water quality. Any non-public water system is ultimately the responsibility of the owner/operator.

Websites:

http://www.slowsandfilter.org

http://www.roofwaterharvesting.org

http://www.shared-source-initiative.com/biosand_filter/biosand.html

 

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2 Responses to Potable water from a DIY slow sand filter?

  1. filter_guy says:

    Excellent question. Thank you. I have no experience with calcium carbonate removal by a slow sand filter, so I can’t tell you what would happen. My post was somewhat misleading, as I have not included all the information. I’ll correct that shortly.

  2. sandy rice says:

    I see sodium is listed as filterable. I live in AZ w much calcium carbonate in the well water. If sand filtering would remove this annoying salt, I could filter enough well water to feed the swamp cooler between rainy seasons. Normally the swamp cooler fed by well water gets caked with the salts which clog the pads and basically corrodes and coats the system in a short time. I’d like opinions to the viability of using sand or other types of filters for calcium carbonite, a fine salt. would the salt clog sand sooner than other filtered materials? Thanks