A fluid level control valve has a base [102] with an aperture [126] formed therein. A cover [120] is slidingly disposed over the aperture [126] and is biased by a thermostatic element [108] in a direction tending to close the aperture [126]. In one embodiment the thermostatic element [108] is an elongated strip having one end captured by tabs projecting from the base, and an opposite end is captured by a bracket formed on the base. The thermostatic element [108] is formed with a V-shaped force imparting portion which is aligned with the cover [120] and the position of the bracket is adjustable to place a selected force on the cover [120] through the thermostatic element [108]. The calibrated valve is then fixedly attached to a housing with the aperture aligned with an aperture in the housing. In another embodiment a U-shaped thermostatic strip has one end mounted on the base with its opposite end biased against the cover.