Bleed Valve Symbol

bleed valve
a valve that releases air from the central heating system.
Used to manually turn on an automatic valve. a bleed valve is located on or near the top of the valve. It can be a small screw, a lever, or built into the solenoid. When turned, the bleed valve allows water to flow out of the cavity over the internal diaphragm of the valve.

symbol
A thing that represents or stands for something else, esp. a material object representing something abstract
something visible that by association or convention represents something else that is invisible; "the eagle is a symbol of the United States"
A shape or sign used to represent something such as an organization, e.g., a red cross or a Star of David
an arbitrary sign (written or printed) that has acquired a conventional significance
The typographic character @, called the at sign or at symbol, is an abbreviation of the word at or the phrase at the rate of in accounting and commercial invoices (e.g. "7 widgets @ $2 = $14"). Its most common modern use is in e-mail addresses, where it stands for "located at".
A mark or character used as a conventional representation of an object, function, or process, e.g., the letter or letters standing for a chemical element or a character in musical notation