Monolithic Permanent Fabric Water Tanks The interior of the revetment with the fabric tank in place ready to be filled with water. The objects on top are weights put in place to force the water to empty properly. Also on the top left is an air vent. The center tubing is a drain put in place to drain rain water from the top of the tank. A Monolithic Fabric Water Tank shown from above with fabric form in place and tank filled with water. Cutaway of a Monolithic Fabric Water Tank showing the interior after tank is filled.