Water-powered sump pumps are normally used to back up conventional electric sump pumps in the event that the building loses electrical power. They are powered by city water pressure, and most units pump 2 gallons out of a basement sump for every 1 gallon of city water used. Water-powered jet pumps eject water under pressure directly into the center of a venturi, which is a smooth reduction in a pipe’s size. The combination serves to create a vacuum to draw water from the sump and eject it under low pressure to outside.
Water-powered sump pumps do not require electricity either to actuate them or to power them. Instead, they are actuated either by a mechanical float valve, or a hydraulic water valve. When the float rises to a high level, the float comes up, and the water valve is turned on to a full position. The city water flow then proceeds to the water-powered venturi to draw out the water in the sump. This unit uses an industrial-grade, plastic, 1-inch NPT float valve to supply enough water to draw the water out of the sump sufficiently. The venturi consists of a length of 1 1/2-inch-wide polyvinyl chloride (PVC) pipe that is smoothly reduced to ¾-inch wide for several inches then enlarged again. A 5/8-inch wide tube ejects a high-pressure, high flow of water into the venturi throat. A little experimentation will determine exactly how far into the venturi constriction the tube needs to go.
The project requires a length of 1 1/2-inch and 5/8-inch wide white Schedule 40 PVC pipe and a 1 1/2-inch to ¾-inch wide reducer. If the reducer has sharp internal corners, they need to be smoothly rounded and sanded until there is no roughness whatsoever. After the reducer, the pipe needs to expand again, and so another reducer is required. A 1 1/2-inch Schedule 40 T allows you to introduce the suction tube. The float-based water valve is available at several websites that offer industrial plastic valves. Check valves are needed in the same pipe sizes for the city water line, as well as the venturi pipe line.
Putting the unit together begins with assembling the T to the 1 1/2-inch pipe on the bottom and one of the sides. Then cement a reducer into the open port. File out the retainer ridge from inside the reducer so that the 5/8-inch tube goes right through the T and to the venturi. The other end of the ¾-inch tube is next joined to the outlet of the on-off float valve and beyond that to the smaller check valve to isolate the system from the inflowing city water. The outlet of the venturi is directed outside the building. The inlet runs through the larger check valve right before entrance to the venturi.
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