Single Line Jet Pumps & Water Wells, Explanation & Repairs InspectAPedia® -
Single Line Jet Pumps & Water Wells, Explanation & Repair Advice
What are the components of a one line jet pump water supply system?
What types of wells use a one-line jet pump for water delivery?
Types of wells and water supply systems and what to watch out for with each
Well pump & water tank diagnosis & repair procedures
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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.
What are the Components of a Shallow Well with a One Line Jet Pump?
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 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.
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.
Many well caps are not water tight, which is why modern drilled well casings extend above ground level.
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 Hand Dug Wells)
a cistern (discussed at Cisterns),
or a spring which includes a water collection pit (discussed at Springs as a Water Supply).
What is a One Line Jet Pump?
A "one-line" jet pump is shown outside of the well, either inside of the building such as the blue water pump in our page top photo or
like this green one line jet pump or perhaps in a well pit or well house. "One line" refers
to the fact that a single pipe connects the pump intake to the well, and the pump has to lift water out of the well and into the building it
serves.
Since the lift capacity of a one-line jet pump is limited to about 27' you can bet that where you find this type of pump installed
it is drawing from a shallow water well.
Our sketch shows the water pump connected to a water pressure tank which in turn supplies water to the
building. The pressure tank is usually located very close to the jet pump but it could be elsewhere.
Pitless Adapter is the special fitting that seals the hole in the well casing where the water piping makes its right angled turn and then
exits the well casing to pass on to the building.
Water piping to the house rises vertically inside the well casing from the top of the foot valve (see below) to a point (below the frost line in
cold climates) where it makes a right angled turn and passes out through the well casing and onwards to the water pump and pressure tank.
Well casing is in this sketch the 6-inch diameter steel pipe which is driven into the well from above ground into bedrock, then sealed against
groundwater leaks.
Foot Valve is a one way or anti-siphon valve which is installed on the pick-up end of the water pipe near the bottom of the well.
The foot valve prevents water from flowing backwards out of the jet pump and well piping back into the well when the jet pump stops operating.
You can see Carson Dunlop's sketch of a foot valve here.
If the foot valve is leaky and water runs back into the well we increase the wear on the water pump as it has to run more often, and pretty soon
the water pump will lose its prime (water inside the pump mechanism) and it may be unable to retrieve any more water from the well whatsoever.
When a shallow well appears to have "run dry" one of the first things to check is whether or not the foot valve needs to be replaced.
Foot Valve Clearance from Bottom shows that the well piping and foot valve are inserted into the well some distance from the very bottom of
the well (inches to a few feet). We need this clearance to reduce the tendency of the well pump to pick up mud and debris from the bottom of the well.
Static head shown in this sketch is the height of the column of water inside of the well between the bottom of the foot valve and the
top of the water when the well is at rest. We discuss "static head" and well recovery rates in detail at How Much Water is In the Well?
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Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
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