Standing Column Wells are the most common in areas with near-surface bedrock and are employed in approximately 80% of the geothermal wells in the northeast. Often these geothermal wells are also employed for domestic and/or irrigation purposes. Domestic Standing Column wells are typically 6 inch rock bores with 8 inch casing pocketed into the bedrock to assure segregation of surface water from pure groundwater. Well bore depths provide the design heat transfer required to satisfy the buildings dominant heating or cooling load.
A “bleed” systems provides the advective insurance that miscalculations in rock thermal characteristics, building insulation values not being achieved, weather extremes beyond Federal standards and the like can be mitigated. Small amounts of advective water drawn from the earth surrounding the borehole stabilize the well bore temperatures by drawing in constant temperature bedrock water from 40-50 feet away. Should additional bore temperature stabilization be required, an automatic “bleed” overflow of typically 5%-10% ensures fresh and temperature constant water is drawn into the water column. Advective bleed periods are typically 30-60 minutes favorably changing the well bore temperature by 4-5 °F
Commercial Standing Column Wells may utilize larger diameter casings and bores.