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All wells must be constructed by licensed well drillers in accordance with state regulations. The well must pass inspection and the water should be certified as potable (drinkable) by the health department before the well can be used. The components of a typical domestic well are as follows:

Casing:  A metal or plastic pipe used to line a portion of the bore hole. The minimum length (depth) of the casing is determined by state regulations based on the geology of the area. In Maryland it is currently 40 feet, or to bedrock. The casing must extend a minimum of 8 inches above the ground (24 inches in flood zones) to keep water runoff out of the well.

Grout:  Material used to provide a watertight seal between the bore hole and the casing to prevent surface water contaminants from running down the side of the well and contaminating the well water.

Well cover:  A cap that screws or clamps onto the top of the well casing to prevent contaminants from entering the well.  If earwigs are a problem, an earwig shield should be installed.

Screen:  A pipe-like attachment at the bottom of the well.  Well screens are usually not required when drilling in bedrock, but they may be necessary if loose sand or fragmented rock is encountered.

Pump:  Draws water from the bottom of the well and into the distribution system.  The two most commonly used types are submersible and jet pumps.

Pitless adapter:  Provides a frost proof and sanitary hookup between the water line inside the well and the household  water distribution system.  The pitless adapter must be located below the frost line and needs to be leak free.



Most residential wells are replenished by rainfall that enters the ground within a few miles of the well. For this reason, the way you and your neighbors use the landscape can be an important factor in the quality of your water supply. Be alert to possible sources of well contamination such as animal wastes, fertilizers, pesticides, septic systems, leaking underground fuel tanks, landfills, and industrial spills or discharges.

Detecting groundwater contamination requires regular testing. You should test your water supply once a year for bacteria and nitrates. Consider seasonal testing if one sample shows elevated levels of these contaminants. Often, periods of heavy rain will flush contaminants into groundwater supplies.

At the least, test your water any time you notice unusual odors, colors, or cloudiness, or if you note an interrupted supply, such as pumping air or sediment. Contact your health department water quality division for information on which tests might be appropriate and to request a list of state certified water testing laboratories.



  • Keep surface water runoff from puddling around the well. Grade your lot so that water drains away from your well casing.
  • Prevent surface water from seeping down the sides of your well. Make sure your well cap is not cracked and is tightly secured. If water tests show contamination, it is recommended that a well driller check the grout and the pitless adaptor.
  • If your well is more than 30 years old, have it inspected by a county health department sanitarian or a qualified well driller to make sure that the casing is not cracked or corroded.
  • Install anti-backflow devices on all faucets with hose connections, or maintain an air space between hose or faucet outlets and the water level in the container you are filling. Otherwise, you risk sucking contaminated water from laundry tubs, swimming pools, etc., back through the plumbing and into your well.
  • Test your fuel oil tank for leaks, especially if it is installed underground.
  • Do not use gasoline, automotive products, solvents, pesticides, or fertilizers near your well.
  • Fecal wastes from both domestic and wild animals deposited close to the well could result in contamination.
  • Be careful never to hit the casing with a lawn mower or strike it with any force.
  • Maintain your septic system. Improperly functioning septic systems can be a major cause of well contamination.
  • Disinfect your well with a chlorine solution anytime work is done on the well or pump. Directions are available from your county health department.
  • If there are unused or abandoned wells on your property, make sure they are properly sealed to prevent direct contamination of ground water by surface contaminants.