A water heating and treatment system with UV lamp and anti-scale water treatment sanitation for suppression of pathogens and undesired bacterial content in a domestic hot water system includes an anti-scale device, and a UV sanitation lamp. A single or multiple mixing station supplies heated water to one or multiple temperature zones. A water heater sanitation loop includes a sanitation loop pump to circulate hot water within the water heater. A three-way return water diverter valve allows for safe sanitation of a domestic hot water system by diverting over temperature re-circulated water away from the mixing valve to a drain, as needed. A method for treating hot water to suppress pathogens and undesired bacterial content in a domestic hot water system is also described.