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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONTAMINANT LEVELS
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
This article describes the components of a one-line jet pump water system, what the components look like, and what they do.This article also describes Single Line Jet Pumps & Water Wells, Explanation & Repair Advice. We provide advice about what to do when things go wrong.
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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's sketch shows the difference between a 'deep well' and a 'shallow well'.
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 at DEPTH of a WELL, HOW TO MEASURE.
An Explanation of the Parts of a Shallow Water Well
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 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.
What is a One Line Jet Pump?
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.
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:
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.
Readers of this document should also see our other diagnostic guides for water pumps, wells, motors, in table form:
Readers of this document should also see WATER PUMP, ONE LINE JET OPERATION, and see Water Tank Types and before assuming that a water problem is due to the well itself, see Water pump and pressure tank repair diagnosis & cost which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost. If your building has water pressure problems, see WELL WATER PRESSURE DIAGNOSIS. Readers whose wells simply run out of water should also see How to Test Well Water Quantity and see How to Get More Water From a Well. If your well pump won't start see ELECTRIC MOTOR OVERLOAD RESET SWITCH for some electric motor or pump motor troubleshooting suggestions.
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Questions & answers or comments about shallow wells and single line jet pumps: installation, plumbing, operation, diagnosis, repair
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
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.
Details about well casing air vent tubes and pipes
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
Questions & answers or comments about shallow wells and single line jet pumps: installation, plumbing, operation, diagnosis, repair.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Water Supply & Drain Piping, Wells, Pumps, Water Supply Equipment