Easy to install - just lower the flexible tube with chamber to the tank bottom (permanent installation). Level can be checked at any time in tanks large and small by the finger operated pump on your NORMOND level gauge up to 120 metres away! The principle is simple. As the mass of fluid in the tank increases, the increased pressure forces a little fluid up into the capillary. The pressure required to expel the fluid registers on the level gauge. A simple but very sound and reliable principle.