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/
http://www.slowsandfilter.org/filter_five.shtml
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.
Many thanks, Mr. Tarsi! Finally got my slow sand filter up and running. Haven’t got the output tested yet but it sure looks pure!
I pretty much copied your design, but I did change a couple things:
1) I use your recirculation pump idea to keep the raw water coming in from the rainwater cistern, but I pump up an expansion tank with the incoming water and then use two misters from the tank to slowly introduce (now highly) aerated water into the filter. There is a 50 micron spin sediment filter before the pump to keep the debris from clogging the 100 micron misters.
2) I use a T-Valve between the cistern and the pure water tank so that I can get a pretty exact ratio between the rooftop water from the cistern and the purified, recirculated water. (I put a meter on the incoming cistern water) The mix then goes back to the filter. There is a check valve that does not allow water from the cistern to mix with the purified water.
3) I’m using a programmable relay timer running for a few minutes every few hours that’s enabled with a normally closed float switch in the purified water tank. If the purified water tank gets too high, the relay won’t run the pump.
There’s more; I plan on posting pics and whatnot on a yet-to-be-named website shortly.
Couldn’t have done it without your help
Thank you for sharing your modifications, John!