Sketch of a drilled well installationPitless Adapters for Steel Casing Water Wells

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Well piping pitless adapters:

This article defines the pitless adapter and explains the use of the pitless adapter on drilled wells that use a steel well casing, modern drinking water wells. The pitless adapter allows passage of well piping out through the side of a well casing at a point underground and without leaks where the pipe passes through the round well casing side. Well piping pitless adapters eliminate the need for a well pit to protect pipes from freezing.

The pitless adapter also permits pulling out of well piping, foot valves, and submersible pumps directly through the top of the well casing. Our page top photo shows a not-very-deep installation of a pitless adapter during parts replacement.

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Pitless Adapter for Drilled Wells

Pitless adapter sketch (C) InspectApediaThe water pipe leaving this well to carry water to the building will be buried below ground, and in freezing climates, below the frost line. A special fitting, the "pitless adapter" is used to seal the passage cut into the round well casing to permit the water piping to pass through the casing and out to the building it serves.

[Click to enlarge any image]

Our illustration at page top and at left shows a low-pressure well spool using a clamp-on pitless adapter in a design suitable for artesian wells whose head pressure is equal to or less than 5 psi (a head of 11.5 ft.) - courtesy Michigan DEP. Similar pitless adapter fittings accomodate other well casing and piping designs.

Other clamp type fittings used at the top of a well casing may be used to seal the well top around piping that exits at the top rather than the side of the well casing. This approach is suitable only in non-freezing climates or where the well head is protected from freezing by its location such as in a well pit or inside of a heated structure.

One of our readers was having trouble pulling the pump and piping up out of their well - the pump jammed in the casing near the top of the well. We wondered if the pump was unable to pass by the pitless adapter since this fitting intrudes into the well casing.

Most modern drilled wells for residential properties use a 6" steel casing which is inserted into the drilled hole prepared by the well driller and then sealed at top and bottom against contamination by surface water or surface runoff.

The best way to locate a well and well casing to avoid surface water contamination is shown in this illustration.

You can figure on about 1.5 gallons per foot of depth of a well using a 6" well casing - but remember you have to find the height of water column available to the pump. Except in artesian walls the water column does not extend from the well bottom to the top of the ground.

Key to our sketch of the parts and features a drilled water well

Sketch of a drilled well installation

In my ugly well parts sketch shown above I've marked the pitless adapter location showing where the well piping leaves the well casing through the casing side.

What's cool about most pitless adapters used on water wells is that inside the well casing the component of the pitless adapter that attaches to the top of the well piping is designed to simply slide up and out of the remaining pitless adapter parts bolted and sealed to the casing side.

Pitless adapter being pulled from a drilled well steel casing in Two Harbors MN (C) Daniel Friedman

This feature is what allows us to pull the well piping and submersible pump or foot valve completely out of the well without having to dig up and expose and disassemble the pitless adapter from outside the well.

Our photo (above-left) shows the mating face of a pitless adapter just after the well driller pulled the well piping and pitless adapter slip fitting up out of an existing well.

This well installation was in Two Harbors, Minnesota where the freeze depth can be so severe that many installers put the pitless adapter eight feet below the ground surface to be sure it and the exiting well piping are below the frost line.

This pitless adapter was not leaking, but this is a place we'd check for leaks if we were looking for a leak in well piping.

Well Casing Top Clamp Fittings Seal Around Well Piping, Wiring, Vents

Other clamp type fittings used at the top of a well casing may be used to seal the well top around piping that exits at the top rather than the side of the well casing. This approach is suitable only in non-freezing climates or where the well head is protected from freezing by its location such as in a well pit or inside of a heated structure.

Well casing top seal (C) Daniel Friedman

Our photo above shows a top-sealed well casing that is designed to permit a single well pipe and some wiring to pass out of the top of the well casing. This well was located indoors in a New York home - not a great idea - in the building basement. From what we see, a single water pipe exiting the well and wiring entering the well, we expect to find a submersible well pump installed here.

Well casing top seal (C) Daniel Friedman

Our second photo (above) shows how a compression type well casing top seal works: bolts tightened through the outside top of the seal compress a rubber gasket between two steel plates. The expanding rubber gasket seals around pipes, wiring conduit, or whatever fittings were designed to pass through this well cap. This well casing top was installed in Two Harbors MN.

Below we illustrate a conventional sealing well casing top cap used where only electrical conduit must enter the well casing above ground. At this well the water pipe exits below ground using a pitless adapter.

Above ground well casing top cap sealing submersible pump wiring (C) Daniel Friedman

Reader Question: how do I protect the well water piping in the well from freezing?

When draining the water from a dwelling that is allowed to freeze, how does the water supply from the submersible pump, supplied with foot valve, drain so the at or above grade pipes don't freeze and break? - Nate

Reply: well piping and pitless adapter should be below the frost line


Freeze protection for the submersible-pump well: in a modern submersible pump or even jet pump drilled well with a steel casing, the water line exits the side of the casing below the frost line (through the pitless adapter). The well piping too, should be buried below the frost line. If well piping is too shallow, indeed it may freeze up in very cold weather.

Water piping exiting older wells in some areas were protected from freezing by constructing a well pit that kept the well head far enough below the ground surface to avoid freeze-ups. But well pits can still permit a freeze-up in prolonged and very cold weather. Operators & owners of buildings served by well pits typically provide a small heat source in the well pit to keep temperatures above freezing. Sometimes a simple light bulb is enough.

More tips about protecting a building from freeze damage are organized at WINTERIZE A BUILDING.

Question: what's the best tool for cutting the well-casing hole for a pitless adapter?

(Apr 28, 2016) George said:
What happens to the metal filings when the hole is drilled for the pitless adapter?

What is the best hole saw to use for drilling a hole for a pitless adapter ?



A bit of metal debris probably falls into the well when the pitless adapter hole is cut using a metal hole saw or a welding torch. Provided the pump is several feet or more above well bottom (as is normal to avoid sucking up mud and dirt), that debris ought to be harmless.

According to Merrill who produce pitless adapters and kindly publish pitless adapter installation instructions, the usual installation procedure follows these steps:

For a two-hole pitless adapter (used with 2-line jet pumps) you'll need to inscribe a vertical line down the casing and to measure the proper distance between two center punches so that the two drilled holes will be located correctly to fit the two-hole pitless adapter.

Resources for pitless adapters: buy, install, specifications


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