DHW

DHW stands for Domestic Hot Water, referring to water that has been heated for household use such as bathing, washing dishes, cooking, and cleaning. It is supplied through a building’s plumbing system and is separate from the cold water supply. DHW systems aim to deliver hot water reliably while minimizing energy use and heat loss.

Common configurations for generating and storing DHW include storage tank systems, tankless (on-demand) systems, hybrid or heat pump water heaters, and solar thermal systems. Storage tank systems hold hot water in an insulated tank heated by electric resistance, gas, or other fuel sources. Tankless systems heat water as it flows through a unit, reducing standby losses. Hybrid systems combine tank storage with heat pump technology for higher efficiency. Solar thermal setups use collectors to preheat water, typically backed by a conventional heater. In larger buildings, district heating or combined heat and power may be used.

Key components typically include the water heater or heat source, an insulated storage tank, cold water inlet and hot water outlet, pressure relief and expansion devices, shutoff valves, an expansion tank, and sometimes mixing or thermostatic valves to regulate outlet temperature. Recirculation lines may be installed to shorten the time to reach hot water at fixtures.

Temperature, safety, and efficiency: Many systems store water at around 60°C (140°F) to limit microbial growth, with mixing valves at taps to reduce scald risk. Codes and standards regulate installation, venting, insulation, and thermal expansion. DHW energy use is a major portion of household consumption, driving demand for high-efficiency heaters, insulation, and supplementary technologies such as solar or heat pump options.