(a) A sludge transfer pump size must be based on the quantity and character of the solids load.(b) A mechanical pumping system must provide the required firm pumping capacity with the largest sludge pumping unit out of service.(c) A centrifugal sludge pump must have a positive suction head, unless the pump includes a priming device.(d) A positive displacement pump or other type of pump must have demonstrated solids handling capability for handling sludge.(e) A positive suction head of 24 inches or more is required for all sludge pumps.(f) An air lift pump may be used as a sludge pump, and must comply with requirements of §217.162 of this title (relating to Air Lift Pump Design).