Jets

Jets

THE JET PRINCIPLE

Jet pumps operate on the basis of the ejection principle. According to this phenomenon, a partial vacuum is created when the velocity of a stream of water is increased by passing it through a constricted nozzle.

The action is identical to that of a garden hose.

In jet pumps, this principle is adapted by means of a device known as ejector.

This unit has three main parts:

Body

Nozzle

Venturi tube

Water supplied by a centrifugal pump flows through the nozzle, creating a partial vacuum.

Atmospheric pressure then forces well water into the system through the side opening of the nozzle.

This "pumped" water, together with the "drive" water from above, then flows through the venturi tube where the velocity is reduced and the pressure increased.

Advantages of Jet Pumps

The operating principle has numerous advantages for private water systems:

Smooth and continuous action (no surges like older pumps.

Can handle unlimited amounts of air

Simple operation with pump impeller as the only moving part

Types of Jet Pumps

SHALLOW-WELL JETS

As indicated earlier, 25 ft is the practical lift limit for any type of pump operating on pure suction.

While straight centrifugal pumps are not efficient to this depth, a unit employing the ejector principle can function efficiently down to 25 ft.

Such a pump, known as a shallow-well jet, has the ejector unit mounted directly on the pump body.

Water from the centrifugal pump is driven through the nozzle, creating sufficient vacuum to suck water from depths up to the full 25 ft.

DEEP-WELL JETS

When water must be pumped from depths greater than 25 ft, the ejector unit is submerged in the well.

In this arrangement (deep-well jet), water enters the ejector as the result of suction, but suction is only partially responsible for its ability to travel to the surface.

The principal factor is the force of the "drive" water being pumped by the centrifugal unit.

Because deep-well jets force rather than suck water to the surface, there is no theoretical limit to their depth capability.

However, submersible pumps normally provide greater cost-efficiency at depths much over 200 ft or even less.

CONVERTIBLE JETS

Some jet pumps are built with ejectors that can be used either:

Mounted on the pump (shallow-well configuration)

Removed for installation in the bore hole (deep-well configuration)

Such units are known as convertible jets and have become increasingly popular due to their flexibility.

MULTI-STAGE JETS

A jet with one impeller is a single-stage unit.

Greater pressure can be obtained by adding additional impellers on the same rotor.

In this arrangement:

First impeller pumps water into second impeller's housing (increasing pressure)

Water passes through additional impeller(s)

Water arrives at ejector at higher pressure than with single stage

This allows:

Operation in deeper wells

Higher pressure delivery above wellhead

VERTICAL JETS

A special type has impeller(s) arranged pancake-fashion on a vertical rotor directly over the well.

This design offers no major efficiency advantages and is primarily marketed to satisfy regional preferences.