A butterfly valve with a housing having a bypass passage located within the housing of the valve. The passage extends from the normal flow path through the valve, either side of the butterfly valve plate so as to provide an alternative flow path. A cavity is located between distal ends of the passage. A valve head, located in the cavity is configured and arranged to be movable within the cavity between a closed position in which, the distal ends of the passage are fluidly disconnected through the passage and an open position in which the distal ends of the passage are fluidly connected through the passage.
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