Filters for the direct filtration of water

Claim 1

FILTER FOR FILTERING WATER, COMPRISING A HOUSING, A LOWER, COARSE-GRANULATION LAYER IN SAID HOUSING HAVING A RAW-WATER SUPPLY MANIFOLD, TWO SUPERPOSED FINE-GRANULATION FILTERING LAYERS OVERLYING SAID COARSE-GRANULATION LAYER, A FIRST DRAINING DEVICE LOCATED BETWEEN SAID TWO FINE-GRANULATION FILTERING LAYERS FOR REMOVING THE FILTERED WATER WITH THE WATER TO BE FILTERED FLOWING IN COUNTERFLOW THROUGH SAID FINE-GRANULATION FILTERING LAYERS, SAID RAWWATER SUPPLY MANIFOLD HAVING AN INLET TO SAID HOUSING FOR THE WATER TO BE FILTERED BENEATH SAID COARSE-GRANULATION FILTERING LAYER, A SECOND DRAINING DEVICE ASSOCIATED WITH SAID COARSE-GRANULATION LAYER, A PIPE LINE CONNECTED TO SAID SECOND DRAINING DEVICE FOR DELIVERING ONE FRACTION OF THE PRE-FILTERED WATER FROM SAID COARSE-GRANULATION LAYER TO THE TOP OF THE UPPER ONE OF SAID TWO FINE-GRANULATION FILTERING LAYERS, THE REMAINING PORTION OF SAID PRE-FILTERED WATER FLOWING DIRECTLY THROUGH THE LOWER ONE OF SAID TWO FINEGRANULATION FILTERING LAYERS.