Heat exchangers that save energy by heat exchange between a fresh liquid and waste fluids

An apparatus arranged to preferentially temper a liquid by heat exchange with a fluid of indeterminate temperature, the apparatus comprising:

• a tank filled with the liquid and connected to a device that dispenses the liquid;
• and
• a heat exchanger comprising:
• a housing extending through the tank and sealed to the ends thereof;
• a drainpipe connected to a supply of the fluid, the drainpipe extending through the housing with an annular space there between;
• a gasket in the space to create a sealed conduit for the liquid;
• the housing extending from one end of the tank to receive an inlet to the conduit for the liquid;
• the conduit having convection holes for the liquid;
• at least one valve moved by convection to allow or block convection through at least one hole;
• the arrangement being that fluid flowing through the drainpipe tempers the liquid in the conduit which always preferentially tempers the liquid in the tank.