Multiple unit backwashing filter

Claim 1

A MULTIPLE UNIT GRAVITY FILTER COMPRISING AN UPRIGHT CENTRAL CORE, A PLURALITY OF FILTER UNITS, EACH HAVING A HORIZONTAL FILTER BED, AN INFLUENT COMPARTMENT OVER SAID BED, AN EFFLUENT COMPARTMENT BENEATH SAID BED COMMUNICATING WITH AN EFFLUENT CHAMBER, AN INLET THROUGH SUPPORTED AT THE UPPER END OF SAID CORE, SAID CORE BEING FORMED WITH INLET PASSAGES OPERATIVE TO DELIVER INFLUENT FROM SAID TROUGH TO THE RESPECTIVE UNITS, SAID CORE FURTHER DEFINING AN ENCLOSED CENTRAL CHAMBER AND BACKWASH SYPHONS OPENING OUTWARDLY INTO COMMUNICATION WITH THE RESPECTIVE FILTER UNITS BELOW THE NORMAL EFFLUENT LEVEL IN SAID EFFLUENT CHAMBER AND OPENING INWARDLY INTO COMMUNICATION WITH SAID CENTRAL CHAMBER, SAID CENTRAL CHAMBER CONTAINING A SUPPLY OF LIQUID ABOVE SAID INWARD OPENINGS TO PROVIDE LIQUID SEALS FOR SAID SYPHONS, A SOURCE OF VACUUM AND MEANS SELECTIVELY OPERABLE TO PRIME EACH SAID SYPHON BY CONNECTING IT TO SAID SOURCE AND TO VENT SAME BY PLACING IT IN COMMUNICATION WITH THE ATMOSPHERE.