Abstract: An automated primary condensate drain line chlorination system includes a first T-fitting installed in an existing municipal water supply line that contains chlorine and algaecides, a second T-fitting installed between an outlet of an existing primary condensation tray of the central air conditioning system and the existing primary condensate drain line, a water supply line extending between the T-fittings, and a normally closed solenoid valve installed in the water supply line between the T-fittings operatively connected with the electrical circuit of the thermostat and fan motor of the central air conditioning system. The solenoid valve opens automatically upon operation of the fan of the evaporator unit of the central air conditioning system to allow a small amount of water from the municipal water supply line to flow into the primary condensation tray and the primary condensate drain line to prevent the growth of algae and/or fungus therein.