1. A standpipe or storage reservoir at the downstream end of a closed aqueduct or feeder pipe, as for a water wheel, to absorb sudden rises of pressure and to furnish water quickly during a drop in pressure. Also known as surge drum.

2. An open tank to which the top of a surge pipe is connected so as to avoid loss of water during a pressure surge.

In pumping of ore pulps, a relatively small tank which maintains a steady loading of the pump.