Patent ID: 7306736

Claim:
A method of ensuring sterility and preventing contamination of a first fluid delivered through a first conduit from a supply source that contains fresh, unused fluid to a point of use, wherein the first fluid is filtered with a substitution filter assembly before the point of use to produce sterile first fluid, the method comprising: disposing a valve mechanism along the first conduit, the substitution fluid filter assembly being upstream of the valve mechanism, the valve mechanism being positionable between an open position in which the first fluid flows through the first conduit to the point of use and a closed position in which the first fluid is prevented from flowing through the valve mechanism to the point of use; sensing a first flow pressure of the fresh, unused first fluid in the first conduit at a location upstream of the valve mechanism and upstream of the substitution fluid filter assembly; combining sterile, filtered first fluid with a second fluid to form a third fluid at the point of use downstream of the valve mechanism; opening the valve mechanism when the first flow pressure exceeds a reference flow pressure by a predetermined value; and closing the valve mechanism under a preselected condition to prevent the first fluid from flowing to the point of use, the closing of the valve mechanism also preventing retrograde flow of the second and third fluids from the point of use to a location upstream of the valve mechanism, thereby ensuring that the first fluid is sterile and substantially free of contamination, wherein the fluid in the first conduit is divided into a first stream that delivers fresh, unused first fluid to the substitution filter assembly where the first fluid is filtered prior to the point of use and a second stream that delivers the first fluid to a location where the second fluid or the third fluid is dialyzed and the valve mechanism is disposed along the first stream of the first conduit between a location where the first fluid is filtered and the point of use of the sterile first fluid such that the valve mechanism acts on and controls flow of the sterile first fluid in the first conduit downstream of the location where the first fluid is filtered, where a location where the fluid is divided into the first and second streams is located upstream of the valve mechanism and substitution fluid filter assembly such that only the first stream is delivered to the substitution fluid filter assembly.