Abstract: A liquid algaecide solution in a replaceable bottle is connected in a non-pressurized connection to the water recirculation line of the swimming pool; at the input side of the pump. A flow control unit and a siphon check valve unit in a feed line connects the bottom of the bottle to the recirculation line. The algaecide solution bottle is releasably coupled to the feed line for gravity flow. The control unit has a manual control to vary the flow rate and the check valve unit permits only flow into the recirculation line. The bottle is releasably mounted to a pipe of the recirculation line. Commercially available solution bottles have a thread output neck. The control unit has a threaded cap connected to the bottle neck, and the upper end of the bottle has a small opening for gravity flow therefrom. The control unit has a dial control valve for selectively opening a metered passageway for precise discharge of the liquid solution and a flexible line connects the control unit to the check valve unit.