With the energy crunch on, a look at South Dakota's geothermal heating potential has been revived. The Madison limestone which is present in most areas of western South Dakota has long been known to produce water in the 120° to 160°F temperature range with relatively good water. The Madison waters have been utilized as heat sources in limited quantities in two communities of western South Dakota for nearly 15 years with moderate success. The Philip Municipal Water Treatment Plant has supplemented its heating requirements with "homemade" heat exchangers which have experienced severe corrosion. The Midland School District has been using a commercial shell and tube heat exchanger which also has been plagued by severe corrosion