Hot water calorifier is an marine term for a storage vessel that has the capacity to generate heat within a mass of stored water. Hot water calorifier is a heat exchanger which heats water indirectly by circulation pump is over a heating coil or multipie coils. The source of heat can be electric heater or steam, heated by an extemal heat source, contained with in a pipe immersed in the water. the two bodies of electric heaterr or steam do not mix. The size of the heater depends on the size and application of the product containing a hot water calorifier.