Biological Layer – A significant decrease in flow rate means
maintenance is needed. This should not be performed more often than
four times per year.
1. Remove Filter Lid leaving the Diffuser Plate in place.
2. Pour approximately 15 liters of water through the Diffuser Plate until
the water reaches the top rim of the filter.
3. Remove the Diffuser Plate.
4. Using the palm of your hand, lightly touch the very top of the sand
and move your hand in a circular motion 2-3 times. This will cause
captured sediment to become suspended in the water. Do not dig
into the sand. Digging into the sand will cause the biological layer to
become buried, potentially resulting in decreased filter performance,
water discoloration, and odor.
5. Allow sand particles to settle for a few seconds, and then scoop
out most of the water and suspended sediment. Do not disturb the
sand layer. Make sure the top of the sand is flat and level.
6. Replace Diffuser Plate.
7. Repeat steps 2–6 as needed until an acceptable flow rate is
re-established.
8. Wash the Lid and Difuser Plate with soap and water (do not use
chlorine). Rinse with filtered water.
9. Replace Diffuser Plate and Filter Lid.
10. Pour a bucket of water into the filter.
11. Wash your hands with soap and water. This is important since the
biolayer layer on the top of the sand contains pathogenss.
12. If this procedure does not restore normal flow rate after repeated
attempts, remove the top 5–10 cm (2–4 inches) of sand from the
filter and place it in a bucket. Add water, agitate, and wash the
sand. Allow the sand to settle for a few seconds, and then scoop
or pour out most of the water and suspended sediment. Avoid
pouring out or removing any sand. Repeat if necessary. Replace
and level sand in filter. Adjust flow rate as necessary. You will need
to wait 14 days for the biolayer to regrow if you perform this step.
Note 1: This maintenance process should not be confused with
“harrowing.”
Harrowing involves digging the hands/fingers into the sand layer.
Harrowing introduces captured biological material into the
anaerobic sand environment and may cause poor taste, discoloration,
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