A capillary fluid flow valve may include a chamber having a first boundary surface and a second boundary surface defined by a housing. The first and second boundary surfaces may be spaced apart by a gap sized to invoke capillary action between the surfaces. The first surface may be angled relative to the second surface. The chamber may have an inlet port, an outlet port, and an air vent port. The gap at the air vent port may be smaller than the gap at the outlet port and the gap at the outlet port may be smaller than the gap at the inlet port.