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A tank fitting admitting and venting air.
Also known as: Conservation vent symbol, Pressure vacuum valve symbol
On a piping diagram a breather valve is drawn at the top of a storage tank, admitting air as liquid is drawn out and venting vapour as it is filled.
Denotes a valve admitting air into and venting vapour from a storage tank as its level changes.
Contexts: Technical drawing
Protects the tank from both overpressure and vacuum; a tank emptied without a breather can collapse inward.
Contexts: Technical drawing
A small valve outline drawn at the top of a tank with an open line to atmosphere above it.