A bottle trap for a waste outlet, the bottle trap comprising: a trap body defining a trap inlet and a trap outlet, wherein the trap body comprises an upper portion and a lower portion 30, the lower portion being threadedly connected to the upper portion by means of a threaded connection (32 and includes an insert, arranged relative to the inlet and outlet such that flow through the trap is defined by a convoluted flow path between the inlet and the outlet such that, when in use, a water seal exists between the trap inlet and the trap outlet, a one-way outlet pressure valve located on a neck connecting the trap outlet to an upper portion of the trap body, wherein the one-way outlet pressure valve comprises a pressure valve inlet and a pressure valve outlet and a pressure valve member, wherein the pressure valve inlet and a pressure valve outlet lie on different vertical planes and are connected by a flow path, wherein the direction of flow through the pressure valve inlet and the direction of flow through the pressure valve outlet are parallel but displaced apart; wherein the pressure valve member rests on a pressure valve member support, and includes a void above the pressure valve member, wherein the void defines an air pocket, which provides a barrier between the pressure valve outlet and the pressure valve inlet; wherein a pressure valve member lower surface forms a seal with an upper surface of the pressure valve member support, wherein the seal between the pressure valve member and the pressure valve member support is maintained, in the absence of a pressure differential, by gravity, gravity pulling on the pressure valve member to pull it down to engagement with the pressure valve member support; and wherein, when in use, in the presence of a negative pressure differential across the one-way outlet pressure valve, the one-way outlet pressure valve is operable to open to allow air to pass through the one-way outlet pressure valve, wherein the pressure valve member lifts away from the pressure valve member support, to relieve the pressure differential but in the presence of a positive pressure differential across the one-way outlet pressure valve, the one-way outlet pressure valve is operable to close to prevent air passing through the outlet one-way pressure valve, wherein the pressure valve member is pressed into engagement with the pressure valve member support; characterised in that; a polymer diaphragm one-way flow valve provided by a duck bill valve is located within the trap body adjacent the trap inlet, wherein the duck bill valve is housed within the insert, wherein the lower end of the duck bill valve is immersed in the water providing the water seal, wherein the diaphragm one-way flow valve permits flow of fluid from the trap inlet to the trap outlet but prevents flow from the trap outlet to the trap inlet. a trap body defining a trap inlet and a trap outlet, wherein the trap body comprises an upper portion and a lower portion 30, the lower portion being threadedly connected to the upper portion by means of a threaded connection (32 and includes an insert, arranged relative to the inlet and outlet such that flow through the trap is defined by a convoluted flow path between the inlet and the outlet such that, when in use, a water seal exists between the trap inlet and the trap outlet, a one-way outlet pressure valve located on a neck connecting the trap outlet to an upper portion of the trap body, wherein the one-way outlet pressure valve comprises a pressure valve inlet and a pressure valve outlet and a pressure valve member, wherein the pressure valve inlet and a pressure valve outlet lie on different vertical planes and are connected by a flow path, wherein the direction of flow through the pressure valve inlet and the direction of flow through the pressure valve outlet are parallel but displaced apart; wherein the pressure valve member rests on a pressure valve member support, and includes a void above the pressure valve member, wherein the void defines an air pocket, which provides a barrier between the pressure valve outlet and the pressure valve inlet; wherein a pressure valve member lower surface forms a seal with an upper surface of the pressure valve member support, wherein the seal between the pressure valve member and the pressure valve member support is maintained, in the absence of a pressure differential, by gravity, gravity pulling on the pressure valve member to pull it down to engagement with the pressure valve member support; and wherein, when in use, in the presence of a negative pressure differential across the one-way outlet pressure valve, the one-way outlet pressure valve is operable to open to allow air to pass through the one-way outlet pressure valve, wherein the pressure valve member lifts away from the pressure valve member support, to relieve the pressure differential but in the presence of a positive pressure differential across the one-way outlet pressure valve, the one-way outlet pressure valve is operable to close to prevent air passing through the outlet one-way pressure valve, wherein the pressure valve member is pressed into engagement with the pressure valve member support; characterised in that; a polymer diaphragm one-way flow valve provided by a duck bill valve is located within the trap body adjacent the trap inlet, wherein the duck bill valve is housed within the insert, wherein the lower end of the duck bill valve is immersed in the water providing the water seal, wherein the diaphragm one-way flow valve permits flow of fluid from the trap inlet to the trap outlet but prevents flow from the trap outlet to the trap inlet.