By Darrel Dunn, Ph.D., PG, Hydrogeologist
Houses in areas where the high water table elevation is less than one foot below a basement floor generally need a sump pump installed. The water table is roughly the top of the saturated portion of the soil beneath the house. It generally fluctuates up and down seasonally due to percolation of rain and snowmelt. It also has long term trends related to drought and rainy periods. Human activities can also affect the rise and fall of the water table (such as lawn irrigation). The purpose of the sump pump is to discharge enough water to keep the water table from rising to the lowest floor or the foundation footer of the house, thus preventing damage.