A disposable infuser is provided having a source of pressurized liquid contained in a liquid chamber (14). The liquid chamber (141 includes housing (20) defining an access aperture (83). A oneway duck-bill valve (80) is contained in the access aperture (83). A separate outlet conduit (84) is provided having a blunt cannula (98). When the outlet conduit (86) is attached to the housing (20). the blunt cannula (98) extends into the duck-bill valve (80) sufficiently to open the duck-bill valve (80) to establish fluid communication between the source of pressurized liquid (14) and the outlet conduit (84).