Benefits of GRP Water Tanks: The demand for drinking water continues to grow rapidly. Within the next two decades, it is estimated that there will be a 50% increase in the demand for drinking water. The need to access drinking water has led to the development of a number of different technologies. One of these is group water tanks or Grp Water Tanks as they are also known. These tanks are smaller in size than individual storage tanks and require fewer resources and lathe bor to manufacture and install.