Single Line Jet Pumps & Water Wells, Explanation & Repairs
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Refer to our sketch of a shallow well (less than 20 feet deep) served by a one-line jet pump located apart from the well. This list and definition of water well parts and terms is organized from the top of the drawing towards its bottom and uses names that correspond to those shown in our drawing. 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).

• A "one-line" jet pump is shown outside of the well, either inside of the building 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 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" 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. 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 Actually In the Well and How Much Water Can Be Drawn Out.