Well Pits for Access to Well Heads, Pressure Tanks, Pumps, Controls
What is a Well Pit & Why are Well Pits Used - sketch & explanation
Well Pits for drilled wells
are excavations, usually outdoors, which were dug below to below the frost line (in freezing climates)
to house the well top and sometimes the pump and water tank.
Well pits are an older approach to well construction in climates subject to freezing, in which a well pit was dug to place piping and controls below the frost line. Newer drilled wells extend the casing above ground and use a pitless adapter if the well is in a freezing climate.
The photo above shows a messy
well pit interior with a plastic bucket over a well casing and a glimpse of the water pressure tank. At page top we have a collapsing well pit with no cover whatsoever - a serious falling hazard.
The sketch shown above, courtesy of Carson Dunlop, demonstrates use of a well pit of capping and accessing drilled
wells was used in order to provide ready access to the equipment while also assuring that the water line
between the well and the building it serves was protected from frost.
While the sketch places the water pump and pressure tank inside the building, in many instances the well pit may contain all of these items.
At left is a photo of an ugly well pit with a bucket covering the well head - what does that tell us?
Well pits are very common in many
areas all over the world.
Well Pit or Well Vault Construction Standards:
Current standards recommend against constructing a well pit, substituting a pitless adapter instead.
Well Pits or Vaults. The use of well pits, vaults, or equivalent features to house the top of a well casing below ground surface shall be avoided, if possible, because of their susceptibility to the entrance of poor-quality water, contaminants and pollutants.
Well pits or vaults can only be used if approval is obtained from the enforcing agency. A substitute device, such as a pitless adapter or pitless adapter unit (a variation), should almost always be used in place of a vault or pit. - California DWR Chapter 10, 2016 cited below- California DWR Chapter 10, 2016 cited at REFERENCES below
Pitless adapters and units were developed for use in areas where prolonged freezing occurs, and below ground (frost line) discharges are common.
Both the National Sanitation Foundation and Water Systems Council have developed standards for the manufacture and installation of pitless adapters and units. (See Appendix E, Bibliography, Bulletin 74-81.)
If a pit or vault is used it shall be watertight and structurally sound. The vault shall extend from the top of the annular seal to at least ground surface.
The vault shall contact the annular seal in a manner to form a watertight and structurally sound connection.
Contacts between the vault and the annular seal, and the vault and the well casing, if any, shall not fail or cause the failure of the well casing or annular seal.
Where cement-based annular seal materials are used, the vault shall be set into or contact the annular seal material before it sets, unless otherwise approved by the enforcing agency. If bentonite-based sealing material is used for the annular seal, the vault should be set into the bentonite before it is fully hydrated.
Cement-based sealing material shall be placed between the outer walls of the vault and the excavation into which it is placed to form a proper, structurally sound foundation for the vault, and to seal the space between the vault and excavation.
The sealing material surrounding a vault shall extend from the top of the annular seal to ground surface unless precluded in areas of freezing. If cement-based sealing material is used for both the annular seal and the space between the excavation and vault, the sealing material shall be emplaced in a 'continuous pour'.
In other words, cement-based sealing material shall be placed between the vault and excavation and contact the cement-based annular seal before the annular seal has set.
The vault cover or lid shall be watertight but shall allow the venting of gases. The lid shall be fitted with a security device to prevent unauthorized access. The outside of the lid shall be clearly and permanently labeled 'WATER WELL'.
The vault and its lid shall be strong enough to support vehicular traffic where such traffic might occur.
The top of the vault shall be set at, or above, grade so that drainage is away from the vault.
The top of the well casing contained within the vault shall be covered in accordance with requirements under Subsection A, above, so that water, contaminants, and pollutants that may enter the vault will not enter the well casing.
The cover shall be provided with a pressure relief or venting device for gases.
Watch out: Safety Warnings Regarding Well Pits
Well pit covers: As with our concern for dug well safety, a well pit should have a child-safe
cover to prevent falling-in and injury.
Well Pit shock hazards: You should also be very careful of electrical shock hazards when entering a well pit. Often the well pit is wet or perhaps even flooded. In such cases be sure to turn off electrical power before entering in or working in the well pit.
At a property where we broke a water supply fitting we needed to shut off the water pump. The water pump and its controls were in an outside well pit. On opening the pit cover and seeing a foot of water therein we knew better than to jump down into the pit to turn off the pump switch. We used a dry broomstick to push the switch to the off position. We could also have found the main electrical panel and found and turned off the pump circuit there.
Watch for collapsing well pits such as the frost-damaged masonry block pit walls shown at page top.
As we also discuss at DUG WELLS, by HAND, our photo at left illustrates a hand dug well that was converted to a drilled well with a steel casing. The old hand-dug well now serves as a well pit. Notice that there is no protection against surface runoff entering the top of the well casing - a sanitary or water potability concern. This rural well is being used for crop watering in San Miguel de Allende.
Watch out for flooding well pits - especially if the well cap is located in the well pit floor. A well pit that floods risks leaking unsanitary surface water into the well - be sure that the well cap is water tight in these cases, and take steps to keep water out of the well pit.
At a property inspection we observed a well pit housing the well head itself as well as water pump and pressure tank. The well casing had no cover installed. It was raining. Water was running across the property from a pony stable down into the well pit and into the well.
Manure-runoff was entering the drinking supply, making it unsanitary and possibly quite dangerous to the building occupants. The well needed to be sterilized, tested, and provided with a water-tight sanitary cover.
The well pit needed to be protected from surface runoff from the stables. The building occupants needed to be informed immediately that their water was unsanitary.
A rough sketch of a well pit and a compression-type well sealing cap can also be seen at
Components of a Well with a Two Line Jet Pump? or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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"Water Well Standards", [PDF] California Department of Water Rresources, 1416 9th Street, Sacramento CA 95814, TEl: 916-653-5791, DWR Chapter 10, retrieved 2016/06/10, original source: http://www.water.ca.gov/groundwater/well_info_and_other/california_well_standards/wws/wws_combined_sec10.html
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