Water extinguishers function very similarly to the early fire-fighting apparatus, in that there is no chemical reaction taking place when the extinguisher is in use. Instead, pressure is either generated by the user through a pump handle or stored inside the canister until the liquid inside the extinguisher is expelled. Simple water extinguishers run the risk of freezing in cold temperatures, so sometimes anti-freeze solutions were also used.

A general marker of a water or antifreeze extinguisher is a pressure gauge on top of the extinguisher, a pump handle, or a squeeze handle. Many notable brands produced water extinguishers alongside soda/acid extinguishers and foam extinguishers, including Elkhart Brass and American LaFrance.