Abstract: A direct contact gas-liquid heater has a tank filled with a liquid, a submerged burner and a gas distributor. The heater burns a fuel air mixture producing hot gas which is bubbled up through the liquid. A system of liquid level raising and lowering pods or a bellows and reservoir prevents the liquid from sumping back through the gas distribution system to drown the burner when the burner is shut off. The heater has a vacuum pump in the exhaust conduit to create a continuous draft for the gas bubbling up through the liquid and baffles to disentrain liquid from the exhaust gases.