A method and device for filling a container (12) with liquid up to a predetermined level (14). The device includes a cylinder (18) and a piston (34) movable within the cylinder (18) between a rest position and a fill position. A supply of liquid (28) for filling the containe (12) is provided to a first end (40) of the piston (34) at alternating pressures to cycle the piston (34) back and forth between the rest and fill positions. Each time the piston (34) reaches its fill position, supply liquid is added to the container (12). With each cycle the device draws fluid from the container (12) and then attemps to compress the drawn fluid with a second end (44) of the piston (34). When the fluid drawn is gas, the piston (34) can compress the gas to continue moving to the fill position. When the drawn fluid is liquid, the piston (34) can not compress the liquid and thus is stopped to prevent further filling.