| Home-made biological water filter
Use of the filter
The Connors demonstrating a clay pot biological sand filter
Once dirty water has been given to the nadi every day for two to three weeks,
the filter will function effectively so long as the sand is not
During this period the water will gradually improve. If the sand and stones
were well washed, water can be improved a little by the filter even on the first
The nadi for storing clean water should be emptied every three days during
this initial period while water quality is rapidly improving.
Pots for storing clean water should never be used for collecting dirty
When using a new nadi to make a filter, it should be first checked for leaks
which should be repaired using cement.
Never completely fill a new nadi or small cracks will develop. Only half fill
it with water at first, then after two or three hours, fill it completely and
check for leaks.
If the filter gets too slow or stops working, remove the top few inches of
sand from inside the nadi. Wash the dirt out of this sand with water in a bucket
or bowl and then put it back in the nadi.
Make sure that the level of the sand in the nadi is restored to 5 inches
below the bottom of the pipe where it comes through the side of the
When it becomes necessary to clean the sand in the filter it is good if there
is another filter in the community that can be used for the two or three weeks
it takes for the filter to build up its numbers of good microbes after being
Dirty water used for starting off a new or recently cleaned nadi can be put
through the new one, then through an established one if it is necessary to drink