How Does a Jet Water Well Pump Work?

Many people rely on water from a well to supply their homes. For thousands of years, manually operated pumps have been in use--and continue to be used in many parts of the world. In locations with electricity, well pumps commonly have electric motors. The most common well pumps today are jet pumps. Jet pumps are powerful, efficient and reliable.

Jet water well pumps work by suction. The suction is created by producing a vacuum. An electric motor drives an impeller that forces water through a small opening, or jet. This increases the velocity of the water, and when it exits the jet it creates the vacuum that creates the suction. Just behind the jet is a Venturi tube, which is a tube that increases in diameter. As the water flows through this tube, the increase in diameter slows the water down, but increases the pressure. The water used in this process is called the drive water.

Since it is the atmospheric pressure that does the work of lifting the water, there is a practical limit to how deep a well can be pumped by suction alone. Depending on local atmospheric pressure, the limit is approximately 25 feet. Shallow wells can use a single drop setup. In a single drop setup, there is one pipe that goes down into the well and draws the water up to the pump.

Jet pumps can be used at greater depths as well. In deep water, the jet is separated from the impeller, and is placed under water. One pipe supplies water to the jet, and another draws the pumped water up and out of the well. This is called a double drop setup.

Since jet pumps use water to create suction and move water, they must be primed, meaning that there is always some water in the pump. One-way valves in the pipes make sure that water will not drain out of the system.

The pump moves the water to a storage tank that has an air bladder that fills up as water is pumped in, creating pressure. The pressure in the tank is maintained at 40 to 60 pounds per square inch (PSI). The bladder maintains pressure, and when the pressure falls by a certain amount, it causes the switch to activate the pump.

Pumps are rated by capacity, usually given in gallons per minute, and pressure. It is important for the capacity of the pump to be compatible with the output of the well for best operation.