7 components coveredField manual · Sump / Well Pump
Wayne CDU series submersible sump pumps (CDU790, CDU800, CDU980E, CDU1000): quick sheet
Covers: Wayne CDU-family submersible sump pumps with the built-in vertical float: CDU790 (1/3 HP), CDU800 (1/2 HP), CDU980E (3/4 HP), CDU1000 (1 HP), plus listed variants CDU790SS, CDU800SS, CICDU790, CICDU800, CDU980ET and CDU1000ET (confirm the variant on the pump label). Search terms: Wayne CDU, CDU 800, CDU-980E, CDU1000 sump pump, Wayne sump pump won't shut off, Wayne vertical float replacement.
A family of 120 V oil-filled submersible sump pumps that share one layout: motor on top, intake drawn from the top of the volute, and a vertical float riding on a rod inside a guard on the side of the pump. Sizes run from 1/3 HP to 1 HP, all with a 1-1/2 in. NPT discharge. Because the pump draws water from the top, Wayne states no weep (air relief) hole is needed, which is different from most bottom-suction pumps.
Safety first
- Water and 120 V power together: unplug the pump before touching the pit water, the pump or the float. Plug only into a working GFCI outlet; never use an extension cord or cut off the ground prong.
- These are sump (clear groundwater) pumps. If the pit receives laundry gray water or any sewage, treat the water as a biohazard: wear gloves and eye protection, wash up afterward, and refer sewage pits to a sewage ejector setup.
- Wayne lists these pumps for indoor use only.
- A pump that has just run can be hot; let it cool before handling the motor housing.
How it works
When pit water lifts the vertical float to roughly 9 in. above the pit floor, the switch closes and the PSC motor starts. The pump runs until the water falls to roughly 4 in., then the float drops and the switch opens. Those levels are set by the float design and are the same across the CDU sizes Wayne lists.
Water enters through the top-suction intake under the motor housing, is thrown outward by a glass-reinforced polycarbonate impeller in a cast iron volute, and leaves through the 1-1/2 in. NPT discharge. The motor sits in an oil bath with upper and lower ball bearings, and a carbon/ceramic shaft seal keeps water out of the motor chamber.
Flow drops as vertical lift rises. Wayne's published curves, for example: CDU800 about 5,100 GPH at 0 ft and about 3,840 GPH at 10 ft; CDU1000 about 6,100 GPH at 0 ft and about 5,100 GPH at 10 ft. A pump that runs but cannot keep up is often simply undersized for the lift and piping, not failed.
A check valve in the discharge line stops the column of water from falling back into the pit each time the pump stops. Without it, the pump re-pumps the same water and short-cycles.
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