A chemical dispensing apparatus to deliver a treatment solution includes a housing configured to be mounted to a wall surface and main fluid passage fitted with an inlet hose coupling at one end and an outlet hose coupling at an opposite end. A control valve is disposed across the main fluid passage at an upstream location and a flap valve is disposed across the main fluid passage at a downstream location of the control valve. A chemical mixing fluid passage is connected at one end to the first control valve and connected at an opposite end to the flap valve. A siphon tube connects a fluid accumulator and the chemical mixing fluid passage such that a flow of fluid through the chemical mixing passage results in liquid chemical contained in the fluid accumulator being drawn through the siphon tube into the flow of fluid through chemical mixing fluid passage.
