The present invention is generally directed to a system for providing heating, cooling, and domestic hot water (DHW) using a water source heat pump, the system including: a compressor; a source heat exchanger; a load heat exchanger; a DHW heat exchanger; and a DHW storage tank. In some embodiments, the system may be concealable, and mounted between two wall studs. In some embodiments, a water-to-water water source heat pump and DHW storage tank may be mounted between the same wall studs, the system having a width of no more than 14.5″ and a depth of no more than 7″. In some embodiments, in a heating cycle high-temperature high-pressure refrigerant in a gaseous phase is provided to both a brazed plate DHW heat exchanger and a brazed plate load heat exchanger in a parallel manner so one of the heat exchangers receives the refrigerant at a time.