Water level (device)

A water level (Greek: Aλφαδολάστιχο or (υδροστάθμη) [Alfadolasticho]) is a siphon utilizing two or more parts of the liquid water surface to establish a local horizontal line or plane of reference.

The ends are held vertical, and the rest of the tubing lies on the ground or floor.

The water level at each end of the tube will be at the same elevation, whether the two ends are adjacent or far apart, so a line between them will be horizontal at its midpoint and a shed base, building foundation or similar structure laid out using several such lines will be "horizontal" within building tolerances on any scale over which use of a water level is practicable.

Other sources of error include difficulty reading due to meniscus.

Also, this liquid solution can be emptied from a small-diameter tube more easily than plain water.