A self-powered pump for heated liquid is provided. The pump includes an airtight container for containing the heated liquid. A heated liquid inlet pipe extends upwardly into the container such that its end is within the container. A heated liquid outlet is lower than the end of the inlet pipe. A breathing pipe extends upwardly into the container such that its end is within the container and is higher than both of the outlet and the end of the inlet pipe but lower than an interior side of the container top. An opposite end of the breathing pipe is outside the container, lower than the container base, and is received by an open container such that the opposite end can become submerged in heated liquid accumulated within the open container during pump operation. A fluid or liquid heating system incorporating the self-powered pump may operate without external power for the pump.