Photograph of a one line jet pump (C)Daniel Friedman 2007 Single Line Jet Pumps & Water Wells, Explanation & Repairs

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One-line jet pumps:

This article describes the components of a one-line jet pump water system, what the components look like, and what they do.

This article explains how a one-line jet pump works, where one line jet pumps are used, the pumping depth or lift height capacity of jet pumps, and jet pump installation, troubleshooting & repair procedures. We provide advice about what to do when things go wrong with your well pump.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

What are the Components of a Shallow Well with a One Line Jet Pump?

Shallow well sketch (C) Carson Dunlop Associates

By definition, if a one-line jet pump is installed at a building, the well is a "shallow well", possibly a bored well or a hand dug well, or even a shallow drilled well. Here Carson Dunlop Associates sketch shows the difference between a 'deep well' and a 'shallow well'.

[Click to enlarge any image]

Refer also to our sketch just below where we depict a shallow well (less than 20 feet deep) served by a one-line jet pump located apart from the well.

A shallow well might be capable of delivering plenty of water, depending on just where it is located, but there are water quality concerns with shallow wells.

A shallow water well is more likely to receive surface runoff, making it a bit more at risk of contamination by bacteria or any chemical that might be on local ground surfaces such as road salt, fertilizers, or pesticides.

Most "shallow water wells" are less than 30 feet deep (so the foot valve is at 24-feet depth or less) and use an above-ground single-line jet pump to "suck" or draw water up from the well. These pumps cannot pull water from much deeper.

Water from deeper wells is delivered by a 2-line jet pump (also above ground) or a submersible in-well pump.

More about measuring the actual depth of a well is


An Explanation of the Parts of a Shallow Water Well

Photograph of a shallow well jet pump Schematic of a shallow well single line jet pump water system (C) Carson Dunlop Associates

The following list and definition of water well parts and terms is organized from the top of our rough drawing towards its bottom and uses names that correspond to those shown in our ugly drawing.

The nicer drawing of a one line jet pump is provided courtesy of Carson Dunlop Associates and provides additional details about single line shallow well jet pump water systems. First we describe items listed on the right side of our sketch, second we describe items and terms listed on the left side of the sketch.

Buried well casing which is typical for older shallow wells - the well casing top may be above ground, buried and hidden from view entirely, or (luckily) located inside of a well pit (less common).

It is particularly important that the well cap on the casing be water tight since otherwise unsanitary surface water and debris can enter the well casing.

Many well caps are not water tight, which is why modern drilled well casings extend above ground level.

Where Else are One Line Jet Pumps Used?

A one line jet pump might also be installed to draw water from other shallow water supply sources including a hand dug well

discussed at DUG WELLS, by HAND

a cistern discussed at CISTERNS,

a spring which includes a spring box or a spring water collection pit

discussed at SPRINGS as WATER SUPPLY.

What is a One Line Jet Pump?

Photograph of a shallow well jet pump

Air Vents on Well Casings

Reader Question: Describe the Air Vent Piping on Shallow Wells

I have a shallow well about 5 feet from my house under my deck. The pipe bringing in the water goes through a hole in the basement cinder block into a crawl space, then about 30 feet to the pump and all the connections. Through the same hole in the cinder block enters another pipe about 1 inch in diameter. This pipe protrudes into the basement about 1 foot.

During the heavy rains of Hurricane Irene, water was flowing through this smaller pipe into our basement, so I stuffed a rag into it.

Could this be a vent pipe? and the groundwater was so full that it filled the well air pocket and flowed through the pipe? Should I open the well lid and re-direct the vent pipe? Can I keep the rag stuffed in the pipe?

None of the local plumbers did a good job installing years ago and we did not keep in touch with any of them. That’s why I am asking you. - P.H.

Reply: small diameter air intake vents are needed on air-tight shallow well casings

Well casing top © D Friedman at A competent onsite inspection by a well plumbing expert usually finds additional clues that help accurately identify strange pipes or if necessary, diagnose a problem. That said:

if the second smaller diameter pipe is indeed connected to your well casing or casing top, as is often the case, it is very likely an air vent.

In shallow wells it was common practice to include a vent line to allow air to enter the well casing during water draw-down in the well, in order to avoid the flow resistance that the above-ground shallow-well pump would encounter if a vacuum was formed in the well casing by the falling water level.

Our well casing top photo (left) includes a red arrow pointing to the NPT pipe thread that marks the location where an air vent tube would have been connected had one been in use on this well.

The two larger-diameter galvanized iron pipes and pipe caps protruding through the center of this well cap would have been used to connect the two lines of a two-line jet pump.

So this is not exactly your case, but our photo shows where the air vent connects at a well casing top.

Shallow well single line jet pumps can pull up water from a maximum of about 25 feet, so you can see that with these less powerful pumps you'd want to relieve the vacuum.

It's also plausible that during hurricane and storm flooding ground around your well may have been so saturated as to temporarily convert your well to function as an artesian well - delivering water on its own.

You can follow the pipe you asked about back to the well to confirm its connection and location and thus its use.

Well vent © D Friedman at Details about well casing air vent tubes and pipes

Finally, 1" is a bit bigger for a well vent than what I've usually encountered. Often the vent line is a simple flexible copper tube of 1/2" in diameter..

Well casing vent pipes are usually routed to a secure, clean indoor location in order to reduce the chances of well contamination from surface water entry into the casing through the vent.

On occasion we've seen copper tubing break off at the top of a well casing, admitting surface runoff and contaminating the well. We've also found an occasional crimped or clogged vent tube on a well casing.

The result of that problem can be reduced water delivery rate from the well - the jet pump is pulling water against a vacuum.

But on some wells we may find a larger diameter well casing vent pipe installed as a standpipe that looks something like our photo at left


What is the Pumping Capacity in Gallons per Minute for a 1-Line Shallow Well Jet Pump?

Deep well pumping capacity - Water Ace Co.

A one-line jet pump can typically raise water from depths of just a few feet (or "0" depth) to about 25 feet in depth, and at water delivery rates of 4 gpm up to as much as 25 gpm depending on the variables we list below the well pump capacity tables shown.

At WATER PUMP CAPACITIES TYPES RATES GPM we compare the pumping capacities of one line jet pumps, two line jet pumps, submersible well pumps, and other water pumping methods.

A nice example table of shallow well 1-Line Jet Pump Capacities for 1/2 hp, 3/4, and 1 hp shallow well pumps is provided in the Water Ace Jet Pump Installation Manual and excerpted below to illustrate the factors that determine well pump capacity.

Both of the charts below are for one-line jet pumps produced by Water Ace. 1-Line jet pumps intended for shallow well use and made by other manufacturers can be expected to have similar capacities.

Deep well pumping capacity - Water Ace Co.

The Water Ace charts (shown in part above) make clear that the capacity of a one-line shallow well jet pump to deliver water at a given flow rate varies by these factors:

  1. the depth of the well (the bottom scale in the two charts)
  2. the pump horsepower (the color codes indicate pump model and horsepower HP variation)
  3. The well pump model (the right hand table is for the company's more powerful well pump series of 2-line jet pumps)
  4. The condition of well piping, including pipe diameter, length, number of bends or elbows
  5. The presumption that the entire piping system has no leaks

Permission requested, Water Ace Corp. Aug 2010 - Pentair Pump Group.

Watch out: Safety warnings are throughout any pump manufacturer's instructions. Because some pump models are capable of developing internal pressures of more than 100 psi, if your building piping, pressure relief valves, safety controls, wiring, and plumbing are not properly installed, very dangerous conditions including electrical shock, tank explosion, and leaks or floods can occur.

If your building has water pressure problems, see WELL WATER PRESSURE DIAGNOSIS.

Readers whose wells simply run out of water should also see WELL FLOW TEST PROCEDURE and see WELL YIELD IMPROVEMENT

If your well pump won't start see ELECTRIC MOTOR OVERLOAD RESET SWITCH for some electric motor or pump motor troubleshooting suggestions.

Useful Pump Manuals


Continue reading at WATER PUMP, ONE LINE JET OPERATION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see WATER PUMP, ONE LINE JET FAQs - questions & answers about single line jet pumps posted originally on this page




Or see WELL CAPS & COVERS - requirements for sealed well caps & covers, requirements for vents & exclusion of vent requirements for some jet pump installations.

Suggested citation for this web page

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


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Publisher - Daniel Friedman