Flassavatnet is a lake in Rogaland county, Norway. The lake lies on the border of the municipalities of Gjesdal and Sandnes. The lake sits about north of the large village of ÃÂ lgÃÂ¥rd, not far north of the lakes Edlandsvatnet and Limavatnet. The lake is a reservoir with a small dam on the southern edge of the lake. The water level is kept at about above sea level. The reservoir holds about .