6th March 2005 at 11:26 am #592
The filter medium is 50 cm altogether. 5 cm concrete, 5 cm rough sand and 40 cm fine sand, which is the actual filter matrix. Once the filter is installed the user should not move it anymore. If they have to remove sand for cleaning purpose, they have to make sure after they applied the clean sand again, the remaining water level on top of the sand will be 5 cm again (not more and not less). The filter is design in a way that it hold the level itself. The use only must not use more than 50 cm sand for it.
Cleo