A sprinkler adapter comprising: a housing having a first end for connection to a firefighting fluid supply pipe, a second end including an internal passageway extending from the first end to the second end, the internal passageway including a receptacle formed at the second end with an internal thread for a threaded engagement with a fire protection sprinkler and a gasket chamber located between the first end and the internal thread with the gasket chamber and the receptacle being aligned with one another and centered about a central axis A-A; and a gasket disposed in the chamber having an unloaded state within the chamber and a loaded state defined by the threaded engagement of the internal thread and the fire protection sprinkler, the gasket having a circular central opening defining an area through which fluid can flow, wherein the gasket chamber defines an expansion void for receipt of a displaced volume of the gasket in the loaded state of the gasket, the expansion void being located above the gasket in the unloaded state; and wherein the housing comprises a self-supporting monolithic plastic about the internal thread; the gasket chamber comprising a first gasket bearing surface having a circular central opening, a second gasket bearing surface having a circular central opening spaced from the first gasket bearing surface, and an internal wall extending between the first gasket bearing surface and the second gasket bearing surface, characterised in that the first gasket bearing surface comprises a skewed portion that is skewed with respect to the central axis A-A towards the second end and a curved portion formed between the skewed portion and the internal wall, in that the central opening defined by the first gasket bearing surface has a diameter Dia1 that is greater than the inner diameter DiaG2 of the gasket; in that the central opening defined in the second gasket bearing surface has a diameter Dia2 that is greater than the inner diameter DiaG2 of the gasket; and further in that the first and second gasket bearing surfaces (28,30) join the internal passageway at right angles a housing having a first end for connection to a firefighting fluid supply pipe, a second end including an internal passageway extending from the first end to the second end, the internal passageway including a receptacle formed at the second end with an internal thread for a threaded engagement with a fire protection sprinkler and a gasket chamber located between the first end and the internal thread with the gasket chamber and the receptacle being aligned with one another and centered about a central axis A-A; and a gasket disposed in the chamber having an unloaded state within the chamber and a loaded state defined by the threaded engagement of the internal thread and the fire protection sprinkler, the gasket having a circular central opening defining an area through which fluid can flow, wherein the gasket chamber defines an expansion void for receipt of a displaced volume of the gasket in the loaded state of the gasket, the expansion void being located above the gasket in the unloaded state; and wherein the housing comprises a self-supporting monolithic plastic about the internal thread; the gasket chamber comprising a first gasket bearing surface having a circular central opening, a second gasket bearing surface having a circular central opening spaced from the first gasket bearing surface, and an internal wall extending between the first gasket bearing surface and the second gasket bearing surface, characterised in that the first gasket bearing surface comprises a skewed portion that is skewed with respect to the central axis A-A towards the second end and a curved portion formed between the skewed portion and the internal wall, in that the central opening defined by the first gasket bearing surface has a diameter Dia1 that is greater than the inner diameter DiaG2 of the gasket; in that the central opening defined in the second gasket bearing surface has a diameter Dia2 that is greater than the inner diameter DiaG2 of the gasket; and further in that the first and second gasket bearing surfaces (28,30) join the internal passageway at right angles