Castelul de apă (numit adesea și turn de apă) reprezintă o construcție hidrotehnică destinată acumulării apei, dar și reglării presiunii și consumului ei în rețeaua unui apeduct.

A water tower is an elevated structure supporting a water tank constructed at a height sufficient to pressurize a water supply system for the distribution of potable water, and to provide emergency storage for fire protection. In some places, the term standpipe is used interchangeably to refer to a water tower, especially one with tall and narrow proportions.[1] Water towers often operate in conjunction with underground or surface service reservoirs, which store treated water close to where it will be used.[2] Other types of water towers may only store raw (non-potable) water for fire protection or industrial purposes, and may not necessarily be connected to a public water supply.