How Does a One Line Jet Pump Well Water Pump Work?

Single line jet pumps on wells: This article describes the sequence of operating steps in a one-line jet pump water system. The process of diagnosis and the costs of the repair are explained.

How a One-Line Jet Pump Well Water System Works - Sequence of Operating Steps

What happens when you turn on the water at a faucet in a building whose water is supplied by a one-line jet pump? (See the sketch at the top of This article for the basic components of a one-line jet pump system.) Our photograph (left) shows a one-line jet pump installed in a home.

Notice that there is a horizontal pipe with a check valve? That's the pipe leading to the water source. (We explain this check valve

at WELL PIPING CHECK VALVES.)

The vertical pipe rising from the pump is the jet pump outlet connection that sends pressurized water to the water pressure tank and onwards to the rest of the building.

The following steps describe normal operating of a building well pump and water supply system.

In other cases in which the well pump controls are not working properly there is a problem with the controls, pressure tank, pump, or well itself.

See WELL WATER PRESSURE DIAGNOSIS.

1. Turn on building water at a plumbing fixture: open a sink valve, tub valve, or flush a toilet.
2. Water runs out of the supply faucet, into the fixture, down the drain
3. Water pressure and flow are being supplied to the building from a water pressure tank. If we didn't use a pressure tank, because water is not very compressible, the second water was turned on, water pressure in the system would drop below the pump cut-on pressure, the pump would turn on, and probably bring water pressure up to the cut-off pressure quickly, causing short cycling and burning up pump controls or a pump motor.
   
   See WATER TANKS HOW THEY WORK.
4. Pressure in the water pressure tank and in the building piping system drops down to the well pump cut-in pressure. Typically this is 20 or 30 psi on a residential water system.
5. The well pump pressure control switch senses the pressure drop, closes an internal electrical relay switch to turn on the well pump.
   
   See WATER PUMP PRESSURE CONTROL SWITCH.
6. The well pump motor runs, drawing water back into the building from the well by "sucking" water up from a shallow depth (a one-line jet pump can't draw water from much below 25 feet)
7. Water is forced into the building water pressure tank and simultaneously into the building piping and on to the plumbing fixtures.

8. If the pump sends water into the building faster than water is flowing out of the open faucet or plumbing fixture, the pump will "get ahead" of the water flow, successfully pressurizing the water tank, causing the pressure switch to turn off the pump (see step 10 below).
   
   OR
9. If the pump cannot send water into the building faster than water is flowing out of the open faucet or plumbing fixture, the well pump will run continuously and water will flow out of the open faucet or plumbing fixture at a rate limited basically by the pump's water delivery flow rate in gallons per minute.
   
   You'll also find this condition if a building water supply pipe bursts. We say "basically" because the well piping and building piping and faucets themselves offer some back-pressure against the pump's flow rate. In this case, the well pump will continue to run until the building faucets or plumbing fixtures are turned off. At that point ...
10. The well pump pressure control switch senses that water pressure has increased to the cut-out point, opening its switch and turning off electrical power to the well pump. The well pump has re-pressurized the building water tank and piping up to the cut-out or cut-off water pressure.
11. The foot valve closes (at the bottom of the well piping) and/or a check valve located in the building on or close to the well pump closes, preventing water and pressure from flowing backwards down into the well, losing building water pressure and possibly losing pump prime.
    
    See WELL PIPING FOOT VALVES
    and
    
    see WELL PIPING CHECK VALVES
    and if necessary
    
    see WELL PUMP PRIMING PROCEDURE.

How to Diagnose Poor Jet Pump Water Pressure

For our complete water pressure and pump, well, and piping problems diagnostic article list,

seeWATER PRESSURE LOSS DIAGNOSIS & REPAIR.

Separately we also provide

a WATER PRESSURE PROBLEM DIAGNOSIS TABLE.

...

Continue reading at WATER PUMP, ONE LINE JET for a description of the function of each component of a one-line jet pump system or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• IDENTIFY WELL PUMP TANK COMPONENTS
• WATER PUMP, TWO LINE JET
• WATER TANK & PUMP DRAIN & WINTERIZE

Suggested citation for this web page

WATER PUMP, ONE LINE JET OPERATION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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