Overflow outlets for gravity tanks shall not be less than 4 inches below the tank supply and shall discharge at least 6 inches above a roof or within 6 inches of a floor drain or they shall discharge over and above the flood level rim of an open water supplied sink or other approved receptacle having a trap with a diameter equal to that of the overflow pipe.
Overflow pipes shall be properly screened against the entrance of insects or vermin.
Overflow outlets shall terminate in a horizontal position above a roof or in a turned-down position above a sink or receptacle.
Overflows shall be sized as specified in Table P-808.
|Tank Capacity (Gallons)||Minimum Size Drain Pipe (Inches)||Minimum Size Overflows|
|Up to 750||1-1/4||One size larger than supply pipe|
|75 to 1500||1-1/2|
|1501 to 3000||2|
|3001 to 5000||2-1/2|
|5001 to 7500||3||One size larger than supply pipe
(Minimum size 4")