a faucet of the single handle mixing valve type . the faucet includes a housing having a domed housing cap enclosing a valve cartridge having an actuating stem movable along a vertical flow - control axis for varying water flow rate , and movable along a horizontal temperature - control axis for varying the temperature . a handle is connected to the actuating stem . a recess extends vertically along the outer surface of the domed housing cap . a releasable stop member is adapted to engage the recess when the handle is moved along the vertical flow - control axis in its cold water only position , and adapted : to release engagement upon application of a horizontal force . a ramp is located along the lower periphery of the domed housing cap outside of the cold water only position and is adapted to prevent the handle from being lowered into a full off position except when in the cold water only position .