A fluid-tight foot support system (100, 200, 260, 280, 300), comprising: a foot support bladder for supporting at least a portion of a wearer's foot; a pump; a first fluid transfer line extending between the foot support bladder and the pump; a first valve allowing fluid transmission from the foot support bladder to the pump via the first fluid transfer line but not allowing fluid transmission from the pump to the foot support bladder via the first fluid transfer line; a fluid reservoir; a second fluid transfer line extending between the pump and the fluid reservoir; a second valve allowing fluid transmission from the pump to the fluid reservoir via the second fluid transfer line but not allowing fluid transmission from the fluid reservoir to the pump via the second fluid transfer line; a reserve reservoir; a third fluid transfer line extending between the reserve reservoir and at least one of the pump, the fluid reservoir, or the second fluid transfer line; a first fluid flow control system for changing the third fluid transfer line between: (a) an open condition in which fluid transfers between the reserve reservoir and at least one of the pump, the fluid reservoir, or the second fluid transfer line and (b) a closed condition in which fluid does not transfer between the reserve reservoir and any of the pump, the fluid reservoir, or the second fluid transfer line; a fourth fluid transfer line extending between the fluid reservoir and the foot support bladder; and a second fluid flow control system for changing the fourth fluid transfer line between: (a) an open condition in which fluid transfers between the fluid reservoir and the foot support bladder and (b) a closed condition in which fluid does not transfer between the fluid reservoir and the foot support bladder. a foot support bladder for supporting at least a portion of a wearer's foot; a pump; a first fluid transfer line extending between the foot support bladder and the pump; a first valve allowing fluid transmission from the foot support bladder to the pump via the first fluid transfer line but not allowing fluid transmission from the pump to the foot support bladder via the first fluid transfer line; a fluid reservoir; a second fluid transfer line extending between the pump and the fluid reservoir; a second valve allowing fluid transmission from the pump to the fluid reservoir via the second fluid transfer line but not allowing fluid transmission from the fluid reservoir to the pump via the second fluid transfer line; a reserve reservoir; a third fluid transfer line extending between the reserve reservoir and at least one of the pump, the fluid reservoir, or the second fluid transfer line; a first fluid flow control system for changing the third fluid transfer line between: (a) an open condition in which fluid transfers between the reserve reservoir and at least one of the pump, the fluid reservoir, or the second fluid transfer line and (b) a closed condition in which fluid does not transfer between the reserve reservoir and any of the pump, the fluid reservoir, or the second fluid transfer line; a fourth fluid transfer line extending between the fluid reservoir and the foot support bladder; and a second fluid flow control system for changing the fourth fluid transfer line between: (a) an open condition in which fluid transfers between the fluid reservoir and the foot support bladder and (b) a closed condition in which fluid does not transfer between the fluid reservoir and the foot support bladder.