What is a Shallow Well Jet Pump?
Shallow well jet pumps are a type of water pump commonly used in residences where there is no access to a city water supply. They are the first part of the well-water purification system, pulling the water up from the ground. They are the simplest and cheapest form of well pump on the market and their only drawback is that they cannot draw water from more than 25 feet below ground level.
The shallow well jet pump starts with a draw pipe. This is the pipe which is driven into the ground. There are three types of draw pipes: driven pipes, case pipes and surface pipes. Driven pipes are used to plumb the depths of the well to the pump's maximum capacity. Case pipes are more sanitary as the intake is surrounded by a series of water filters to prevent sediment and other impurities being pulled up by the pump. Surface pipes are used in flood-plains or marshes where the water is actually already above ground level. Terminating at the top of the draw pipe is a check valve leading into the pump housing. The pump is a cylindrical design which contains an impeller similar is shape to a fan blade. This fan blade is powered by an electric motor attached to the rear of the pump housing. Leading from the pump housing is a device called a jet, which is a narrowing of the pipe. From there, a safety cutoff valve connects to a venturi, which is a widening of the pipe directly before it connects to the residence's water filtration system and supply.
Shallow well jet pumps work by an imbalance in air pressure, similar to the way that fluid is sucked up a straw. The pump is primed by being poured full of water. When engaged, the impellers in the pump spin, moving the water and air pockets through. The air vents through the emergency cutoff valve to create an area of uninterrupted low pressure, which naturally pulls the groundwater upward. When the water reaches the jet, the narrowed pipe diameter acts to speed water flow all the way to the venturi, which may be some distance away. When in the venturi, the increased pipe diameter causes the water to pool until so much water fills the pipe that it reaches a higher pressure. This pressure is the means by which water flows through the filtration system, hot water heater and out the various taps of the residence.