It is now May 22, 2021. All the original slow sand filters here are still functional. We have 9 slow sand filters running here. Four of them are pond filters. The latest pond filter is still being tested and no data is available. The other 8 filters are still functional. Three of them are pond filters. No tests have been done yet because of the Covid situation.
Filter 1 has been running since 2008: http://www.slowsandfilter.org/
Filter 2 and 3 have been running since 2009: http://www.slowsandfilter.org/
Filter 4 and 5 have been running since 2012: http://www.slowsandfilter.org/
Filter 6 (pond filter) has been running since 2010. It runs 24/7 and has an automatic overflow. The water continues to stay crystal clear: http://www.slowsandfilter.org/pond_filter.html
The other two pond filters have been running about 8 years.
The cistern has been repaired and not leaking; it has been functional since 2010. http://www.slowsandfilter.org/cistern_page.shtml
We did have some snow this winter. The temperatures were very close to typical for this area (Pacific Northwest Washington state). Hopefully, this year, we will be able to do some water quality testing, and flow rate testing.