About this rainwater harvesting blog

Roof water (rainwater) harvesting along with slow sand filters will soon become a necessity rather than a curiosity. This blog is an attempt to increase awareness of water supply options available to the individual, and provide a means for discussion. If you are located in the Pacific northwest part of Washington state, and would like help setting up a rain water /  roof water filtering system leave a message at the bottom of this page in the comment space with your contact information, and we will get back to you as soon as we are able.

The work described here takes place at the edge of the foothills of the Cascade mountains in western Washington state, U.S.A.  about 30 miles northeast of Seattle Washington. All of the testing and work done here is based on the environmental conditions here in this small part of the world. The image at the top of the blog page is Eagle Falls, which is located in the Cascade mountains. The background image is the Pacific ocean beach on the coast of Oregon.

The information posted on this blog by the author regarding the design,  construction, and operation of small slow sand water filters is based largely on actual experience, which has been ongoing for 7 years now; and will continue as long as physically possible. The websites slowsandfilter.org,  shared-source-initiative.com/biosand_filter/biosand.html and   roofwaterharvesting.org are connected with this blog through the same author and similar topics. The study of existing peer reviewed scholarly articles along with documentation from other websites is also used. Links to these sources can be found here, and here.  The tests on water flowing into and out of the filters are done by EPA approved laboratories and the results are posted on the websites noted in the links above. Neither the author, nor this blog are connected with any religious or political group(s) or organization(s).

Please keep your comments and questions relevant to rainwater and/or roofwater harvesting, biological sand filters and sustainable water purification practices studies.

Important: Do not drink the water from any of the filters described in this blog or on the following websites associated with this blog without having the water tested by your local health department. Know that each owner of a filter is totally responisble for its proper operation and water quality. Even if a filter is built exactly like the ones shown on these websites, it is still possible for it to produce contaminated water. This blog, and the 3 websites associated with it, and any communication with the author do not make water 100 percent safe to drink. Public water systems are monitored by professionals and still there are contamination outbreaks that do occur.

Please, do not confuse the devices described on the above mentioned websites with the “Biosand filter”. The Biosand filter is an entirely different design, and has been thoroughly tested in the field and in use. The Biosand filter is NOT EXACTLY the same thing as the filters studied on the websites associated with this blog.
You have been advised.


14 Responses to About this rainwater harvesting blog

  1. Orpheus says:

    The “Target” sand is available from McLendon’s hardware.
    Sumner: 253-863-2264
    White Center:206-762-4090
    Woodinville: 425-485-1363
    Kent: 253-850-2722
    Puyallup: 253-536-6560
    Renton: 425-235-3555
    You will need to ask them specifically for the “Target Filter sand”. Also, the Renton store has a very nice selection of sand from the “Unimin” company. I use the .15 mm effective size sand in several of the filters here. There is an outfit in Renton called “Manufactures Mineral Co.” They are located at:
    1215 South West Monster Road Renton, WA 98057
    (425) 228-2120
    They have .25 mm effective size filter sand in 100 pound bags.

    Salmon Bay Sand and Gravel, in Seattle (Ballard) has the Unimin .15 mm effective size sand in 100 pound bags. They will load it for you.

    The simplest way is to buy sand that is already sifted. However; if you use the “Play sand” from Lowes, you will need to sift it using stainless steel wire cloth. The play sand won’t work without sifting because it has too much inconsistency in the size of the grains – it has lots of very fine and lots of coarse grains. The stainless steel wire cloth is available from Grainger. You’ll need to make a frame out of 2X4’s or 2X6’s to hold the wire cloth. I would use 40 mesh and 60 mesh. Discard the the sand that won’t go through the 40 mesh, then put the stuff that goes through the 40 mesh on to the 60 mesh and keep the stuff that does not go through. The 40 mesh has larger openings than the 60 mesh.

    Update August 13, 2012: After purchasing the “play sand” today, and looking at the wire cloth, it appears that 60 mesh will be way too fine to be used
    on this sand. I will try some sifting asap and post the results as I get time.

    August 14, 2012: The “play sand” is not uniform size, and is a real pain to “sift”. I tried it today, and spent a lot of time fooling around with a 50 pound bag of sand, only to end up with about 15 pounds of uniformly sized washed sand, which was very fine and actually looked good, but the effort was great and the reward tiny. To make a long story short, If you don’t have to sift sand – don’t.

    On the other hand, the sand I ended up with, probably will work for the top “fine sand” part of a slow sand filter, but it will take at least 10 bags of the play sand to get 100 pounds of the fine sand after sifting it, and; if the mixture from the manufacturer of this sand varies even slightly, (as it might since it is not being “packaged” for filtration), the end result could be entirely different; and furthermore, the sand requires huge amounts of water to wash it. To get 100 pounds of this sand sifted and clean will take hours of work, and at least several hundred gallons of water. The mesh sizes I recommend are too fine to end up with .25 mm effective size sand for the bottom part of the sand in a small slow sand filter. 30 mesh might be a better choice. Also, note that different manufactures have different ways of referring to their “mesh sizes”. If you sift this sand dry, ABSOLUTELY WEAR A DUST MASK. THE DUST FROM THIS STUFF IS NASTY- I CANNOT STRESS THIS ENOUGH – WEAR A MASK. Wet, however, it is fairly harmless, with the exception of drying out your hands.
    Dave T
    Snohomish, Wa.

  2. Jim in Seattle says:

    I’m interested in setting up a system like this for vegetable gardening and as an emergency water supply. I’m putting together a parts/cost list. I’ve been unable to source the “Target” fine sand or silica sand online. Would I need to contact a pool supply store? And for the coarse (or ungraded) sand: will regular playbox sand from Home Depot/Lowe’s work?

  3. James says:

    To Author,

    I absolutely love your DIY site, http://www.shared-source-initiative.com/biosand_filter/biosand.html

    My only real question is this: Where do we get those materials?

    I’ve tried going to certain stores but no one seems to carry the PVC or the sand materials you described. In fact, getting the PVC joints seems impossible.

    Who are the distributors for PVC parts?

    Again, create site and thanks for blogging about it.

    Try Lowes, or Home Depot. Also, your local hardware store should have pvc fittings. You can order them online, too. Either Lowes, or Home depot will order sand for you. You can also get sand locally and sift it yourself.
    Posted by Filter Guy

  4. admin says:

    The works cited page on the shared-source site is :
    The works cited page on slowsandfilter site is :

    To cite my work just follow the attribution requirements on this page:

    and this page:

  5. Ben says:

    I was directed here from [http://www.shared-source initiative.com/biosand_filter/contact.html] I don’t know how to contact you otherwise, but I’m conducting a few experiments on alternate water filtration techniques for school, and I need to cite sources. If you could email me your info, I would appreciate it. If you would like more info on my project, feel free to email me.

    Ben H.


  6. Brian says:

    I am in process of building a 1200 gallon concrete rainwater cistern at my home in Portland, Oregon. It will be cut into a hill, so 3 sides against / partially against the soil. A friend questioned whether freezing water would damage the concrete seal or the blocks. Any thoughts or experience?

    • admin says:

      Hi Brian. My thoughts, for what they are worth . . . here goes. Last winter it got down to about 15 degrees here and our cistern did not crack, 1/3 of it is above ground all the way around and it was damp on the outside and leaking on the inside. There was no obvious damage. My best guess would be that if water gets into the cement and freezes there it will crack. Freezing on the outside should not hurt it unless the water can penetrate into the concrete. I would make sure the cistern is sealed completely from the outside as well as the inside. It will have to get really cold for a long time for the water to freeze inside a concrete cistern and I don’t think it will get that cold too often here on the west coast. That said, we did have that cold spell several years ago when it got down to about 5 degrees here. I’m not sure about the Portland area. I hope your cistern works out ok for you.

  7. admin says:

    A good source of information about filters in places other than the U.S. can be found at
    this website regarding the Biosand filter.
    These filters have a design that has been tested by health officials and is known to work.

    There are (at the very least) thousands of pages of studies regarding the “living layer” in a “slow sand filter”. The website slowsandfilter.org has a page with
    a collection of scholarly articles describing, among other things, the known characteristics of the biological activitty in a “slow sand filter” . These studies would be the most authoritative sources of information regarding the biologically active layer of sand.

    As far as the biolayer being frozen, the only step I have taken so far is to wait for the filters to thaw out and start flowing again.

    I cannot tell anyone if the water from any filter is ok to drink. Local health officials are the final authority on that.

  8. Kevin says:

    You mention that the living layer of the filter must always be submersed, but does the water need to be continually aerated/recirculated? If so, do you have any recs. for the recirc. pumps and power sources? You mention in several places that the water from these filters should not be consumed. I was thinking about using something like this for an emergency water filtering system, but is there something else I should be looking into? I’ve seen the slow sand filters being touted in third world countries as a way to filter water and improve human health. If their water is consumable, what might they be doing differently than you that makes their water consumable? You also mention that some of your filters have frozen. What steps are taken to “restart” the filters after they are frozen? Is the living layer completely destroyed, or does it go dormant? Thanks for all your time.

  9. admin says:

    Thank you Rebecca. Getting the barrels set up is the first step. If everyone here in Seattle had rain barrels there would be a lot less (massively less) pollution running into lake Washington, the rivers, and Puget Sound. I did update the links on the original website, and of course it will show up here also. There are two other sites associated with this blog, I suppose I could put links there too.

  10. Rebecca says:

    Hi, David. We had exchanged links a while ago and I wanted to update you that my popular Build Your Own Rain Barrel website has moved to:


    Looks like it’s on this page at least of your site(s): http://www.shared-source-initiative.com/biosand_filter/biosand.html

    Thank you, and Happy Watering!

  11. admin says:

    The part about the pitch of the roof is a bit ambiguous. For a given fixed perimeter or square footage of floor space, as the pitch of the roof increases, the total area of rain catchment surface increases. So more gallons per inch of rain becomes available. For example for a slope or pitch of 4/12 (4 units rise and 12 units run) a certain given amount of runoff is available. If you increase the pitch of the roof to say 8/12 then there will be more surface area of roof to catch water.

    Probably one large filter with a single storage tank would be the best option, as there will be less likely hood of contamination.

  12. Patrick Fallon says:

    Hi, really inspired by your blog, and your instructions of how to make a slow sand filter. I am writing to ask about the pitch of roof, as I didn’t quite understand on the specific details section. I am an architecture student and live in england, UK and am trying to integrate this system into a building I am designing. The site is in medieval Salisbury and the yearly rainfall is 40inches. I calculated that if i had a series of small study pods of 13sq feet over a year they could collect about 900 pints each. Would a pitch increase the need for more roof area? this was what i didnt understand. Also is it possible to have a series of small personal sand filters in these small rooms, or is it always better to have a large storage tank that can be distribited. thanks Patrick