Catheter with back-flow prevention

1. A drainage only catheter comprised of a tube and a coupling assembly; the coupling assembly on a first end is connected to an end of the tube; the coupling assembly on a second end includes a port; the coupling assembly has an interior volume bounded on a first end by a seat and near a second end by a retainer, the coupling assembly is configured to provide that a fluid flowing in a drainage direction enters the coupling assembly at the first end and exits the coupling assembly at the second end; the coupling assembly further including an ultra-low pressure activated valve which prevents backflow at all times, and is activated by flow direction; the seat has a first diameter; the interior volume of the coupling assembly includes a ball which operates at ultra-low pressures in response to a reversal in direction of flow, wherein the ball of the valve is captured between the seat and the retainer in response to a reverse flow, and there is only a minor reverse flow for the time it takes for the ball to move into contact with the seat of the valve within the coupling assembly of the drainage only catheter; the ball has a second diameter; the seat completely encircles the first end of the coupling assembly; the interior volume between the seat and retainer has a third diameter; the first diameter is less than the second diameter, the second diameter is less than the third diameter; the first diameter is less than or equal to the difference between the third diameter and the second diameter wherein in response to an other-than-liquid entering the interior volume, the other-than-liquid passes the ball and exits through the port at the second end of the coupling assembly; the coupling assembly is further configured to provide that any other-than-liquid that fits through the first diameter will necessarily fit through the third diameter and exit the coupling assembly; the ball is configured to freely float in the interior volume between the seat and the retainer; the coupling assembly is further configured to provide that in any orientation, an unpressurized fluid flows in the drainage direction through the coupling assembly and the ball does not contact the seat, wherein fluid flow from the first end of the coupling assembly passed the ball and to the port where the unpressurized fluid exits the coupling assembly of the catheter, the coupling assembly is further configured to provide that in any orientation where the fluid flows in a backflow direction through the coupling assembly, the ball flows into contact with the seat creating a watertight seal between the ball and seat, preventing further flow in the backflow direction except for the minor amount of time that it takes the ball to reach the seat; and permits other-than-liquid to pass through the valve and exit the coupling assembly of the drainage only catheter.

2. The catheter as described in claim 1 , further characterized in that the difference between the second diameter and third diameter is sufficient to provide for the passage of other-than-liquids around the ball in response to fluid flowing in the drainage direction.

3. A drainage only catheter comprised of a tube and a coupling assembly: the coupling assembly on a first end is connected to an end of the tube; the coupling assembly on a second end includes a port; the coupling assembly has an interior volume bounded on the first end by a seat and near the second end by a retainer; the coupling assembly is configured to provide that a fluid flowing in a drainage direction enters the coupling assembly at the first end and exits the coupling assembly at the second end; the coupling assembly further including an ultra-low pressure activated valve which prevents backflow at all times, and is activated by flow direction; the seat has a first diameter; the interior volume of the coupling assembly includes a ball which operates at ultra-low pressures in response to a reversal in direction of flow, wherein the ball is captured between the seat and the retainer in response to a reverse flow, and there is only a minor reverse flow for the time it takes for the ball to move into contact with the seat; the ball has a second diameter; the seat is configured to completely encircle the first end of the coupling assembly; the interior volume between the seat and the retainer has a third diameter; the first diameter is less than the second diameter; the second diameter is less than the third diameter; the first diameter is less than or equal to the difference between the third and the second diameter; the ball is configured to freely float in the interior volume between the seat and the retainer, the coupling assembly is configured to provide that in any orientation, an unpressurized fluid flows in the drainage direction through the coupling assembly of the drainage only catheter and the ball does not contact the seat and unpressurized fluids flow from the first end of the coupling assembly passed the ball and to the port of the coupling assembly of the drainage only catheter; when the coupling assembly is in any orientation and the fluid flows in a backflow direction through the coupling assembly the ball flows into contact with the seat creating a watertight seal between the ball and the seat preventing further fluid flow in the backflow direction except for the minor amount of time that it takes the ball to reach the seat; and permits other-than-liquid to pass through the valve and exit the coupling assembly of the drainage only catheter, the density of the ball is the same as the unpressurized fluid; and the difference between the second diameter and the third diameter is sufficient to allow the passage of other-than-liquids around the ball in response to unpressurized fluid flowing in the drainage direction.