About Jet Pumps
A well jet pump is a non-submersible, non-self-priming, centrifugal type pump which draws water from a water well, pond, lake, underground tank or similar source of clean water. The pump operates by creating a pressure differential with the help of jet ejector (JE) kit, comprised of a nozzle and venturi in a manner similar to the turbines of a jet aircraft.
A jet pump comes with a pressure switch with (in most instances) adjustable On/Off settings. Typical factory pressure switch settings (On/Off) are 20/40 or 30/50 psi. When water pressure in the system falls below the On level (20 or 30 psi), the pump turns on and runs until the pressure builds up to Off level (of 40 or 50 psi).
Jet pump is typically installed near the water source, elevated above the water level, and must be protected from weather and accidental splashing. A foot valve (check valve) is required for most installations to prevent backflow and to allow user to fully prime the suction piping with water prior to operation.
Besides the suction/discharge outlets, a jet pump commonly has at least (3) additional small outlets - one at the top for priming, one at the bottom for drainage and one at the side for installation of a pressure gauge. These are factory-plugged by default and can be utilized as needed.
Jet Pump Types
All jet well pumps can be divided into the following types according to their internal construction and installation specifics:
Shallow Well Jet Pumps
Shallow well type jet pump has a JE kit permanently built into the volute and has a single suction inlet and a single discharge outlet. A shallow well jet pump has a suction lift of 25ft and is intended for applications with relatively high water table and abundant water (high well replenishment rate).
Deep Well Jet Pumps
“Convertible jet pump†and “
deep well jet pump†are interchangeable terms used to describe a jet pump with an external, removable JE kit. When JE kit is attached to the pump, it operates in a “shallow well†mode and has the same capabilities as the shallow well jet pump. When JE kit is detached and installed submerged in a well, the pump is converted to a “deep well†mode, capable of drawing water from down to 80ft depth.
Jet Pump Sizing
There are several important factors to consider when selecting a jet pump:
Water Table
Water table is the most important factor when selecting a jet pump. In areas with a constant, relatively high water table, a standard shallow well type pump is generally adequate to provide constant water supply. In areas with a lower or varying water table, a deep well or convertible pump is needed. Well capacity, standing water level, drawdown water level and regeneration rates are all important specifics which also must be accounted for.
Water Demand
As a rule of thumb, a 1/2 HP jet pump is sufficient to provide water for a small home with a family of 2-3, provided that it is located close to the water source.
3/4 HP pump is used in applications where two water fixtures may be used at the same time, such as a shower and a kitchen sink or a laundry.
1 HP jet pump is used for permanent residence homes with several bathrooms and larger size families.
Pumps over 1 HP are more typical for agricultural or commercial applications with high water demand.
Well Tank
Well tank is a required component for most water well systems, including jet well pump systems. Well tank accumulates well water and holds it under pressure, creating a “pressure cushion†which helps to maintain a steady water pressure at the plumbing fixture (faucet/shower, etc.) and reduces frequent cycling of the jet pump, effectively extending its’ lifespan.
