Bio-sand filters are based on the same filtration system the earth itself is based on. Water added to the top of the filter passes through a large sand bed then through two different size gravel beds.
We use sand and gravel taken from a local riverbed. It is screened and sorted to the required sizes. These layers are then washed and measured into bags that can be stored for transportation to the site where the filter will be installed. A specific flow rate must be attained and maintained. This requires periodic checks to each filter to insure it is flowing properly and providing the safe , clean water desired.