Liquid-cooled electronics racks are provided which include: immersion-cooled electronic subsystems; a vertically-oriented, vapor-condensing unit facilitating condensing dielectric fluid vapor egressing from the immersion-cooled subsystems, the vertically-oriented, vapor-condensing unit being sized and configured to reside adjacent to at least one side of the electronics rack; a reservoir for holding dielectric fluid, the reservoir receiving dielectric fluid condensate from the vertically-oriented, vapor-condensing unit; a dielectric fluid supply manifold coupling in fluid communication the reservoir and the dielectric fluid inlets of the immersion-cooled electronic subsystems; and a pump associated with a reservoir for pumping under pressure dielectric fluid from the reservoir to the dielectric fluid supply manifold for maintaining dielectric fluid in a liquid state within the immersion-cooled electronic subsystems.