What kind of sand and gravel do slow sand filters use?
It is best to use sand that is NSF/ANSI 61 or AWWA 100 approved. If this type of sand is not available, know EXACLTY where the sand and gravel come from and EXACTLY what is in it – and what is NOT in it. Be certain there are no industrial chemicals in the sand and /or gravel. Things like lead, mercury, asbestos, zinc, petroleum derivitives, insecticides, pesticides, or storm runoff residue from road surfaces may be in sand. back to top 11.
It is best to use sand and gravel that is NSF/ANSI 61 or AWWA 100 approved. If this is not available, know EXACLTY where the sand and gravel come from and EXACTLY what is in it – and what is NOT in it. Be certain there are no industrial chemicals in the sand and /or gravel. Things like lead, mercury, asbestos, zinc, petroleum derivitives, insecticides, pesticides, or storm runoff residue from road surfaces may be in sand, or on gravel. Be certain the sand is washed clean of any organic material, clay, mud, or slit. The sand should be washed until the water draining from it is clear. Play sand that has been sterilized can be purchased at most home improvement stores. It will work if the sand is fairly uniform in size. Builder’s sand may work, but if the grains are too coarse and the size is not uniform (see faq 11) it may not work satisfactorily; also be certain chemicals have not been added if builder’s sand is used. The following website has listings of NSF certified sand suppliers an
