A liquid flow control device has a port or passageway through which liquid flow is to be controlled. A body of a liquid swellable material is located in the port or passageway having an upstream side and a downstream side in relation to the direction of liquid flow through the port or passageway. A layer of sealing material is provided on the upstream side of the body to prevent contact of that side of the body with the liquid when the body is swollen to close the port or passageway while allowing contact of the downstream side of the body when the body is in the non-swollen condition allowing liquid flow through the port or passageway.