Abstract: A method and apparatus is disclosed for supplying a fluid under pressure to a channel and for blocking a backflow of fluid from the channel to a catheter. The apparatus is a one-way valve assembly for use with a container supplying a fluid under pressure to a channel. The one-way valve assembly includes a first tube for communicating the fluid into a channel, a valve, and a second tube communicating with the container supplying the fluid and transmitting the fluid to the first tube via the valve. The valve comprises a base member with a hollow interior and a sealed distal end, which hollow interior is capable to communicate the fluid between the second tube and the first tube through at least one slit aperture which is positioned near the sealed distal end of the base member. The base member is engaged and covered by a flexible pressure-responsive surface which seals the slit aperture in order to prevent backflow of fluid from the first tube into the base.